Methods for arranging nanoscopic elements within networks, fabrics and films

ABSTRACT

A method for arranging nanotube elements within nanotube fabric layers and films is disclosed. A directional force is applied over a nanotube fabric layer to render the fabric layer into an ordered network of nanotube elements. That is, a network of nanotube elements drawn together along their sidewalls and substantially oriented in a uniform direction. In some embodiments this directional force is applied by rolling a cylindrical element over the fabric layer. In other embodiments this directional force is applied by passing a rubbing material over the surface of a nanotube fabric layer. In other embodiments this directional force is applied by running a polishing material over the nanotube fabric layer for a predetermined time. Exemplary rolling, rubbing, and polishing apparatuses are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority under 35U.S.C. § 120 to U.S. patent application Ser. No. 13/076,152, entitled“Methods For Arranging Nanoscopic Elements Within Networks, Fabrics, AndFilms,” the contents of which are incorporated herein in their entiretyby reference, which is a continuation-in-part of and claims priorityunder 35 U.S.C. § 120 to U.S. patent application Ser. No. 12/945,501,filed on Nov. 12, 2010, entitled “Methods for Arranging NanotubeElements within Nanotube Fabrics and Films,” the contents of which areincorporated herein in their entirety by reference, which claimspriority under 35 U.S.C. § 119(e) to U.S. Provisional Patent ApplicationSer. No. 61/319,034, filed on Mar. 30, 2010, entitled “Methods forReducing Gaps and Voids within Nanotube Layers and Films” and U.S.Provisional Patent Application Ser. No. 61/350,263, filed on Jun. 1,2010, entitled “Methods for Reducing Gaps and Voids within NanotubeLayers and Films,” the contents of which are incorporated herein intheir entirety by reference.

This application further claims priority under 35 U.S.C. § 119(e) to thefollowing provisional applications, the contents of which areincorporated herein in their entirety by reference:

U.S. Provisional Patent Application Ser. No. 61/449,784 filed on Mar. 7,2011, entitled “Methods for Arranging Nanotube Elements within NanotubeFabrics and Films;”

U.S. Provisional Patent Application Ser. No. 61/350,263, filed on Jun.1, 2010, entitled “Methods for Reducing Gaps and Voids within NanotubeLayers and Films;” and

U.S. Provisional Patent Application Ser. No. 61/319,034, filed on Mar.30, 2010, entitled “Methods for Reducing Gaps and Voids within NanotubeLayers and Films.”

This application is related to the following U.S. patents, which areassigned to the assignee of the present application, and are herebyincorporated by reference in their entirety:

U.S. Pat. No. 6,835,591, filed on Apr. 23, 2002, entitled METHODS OFNANOTUBE FILMS AND ARTICLES;

U.S. Pat. No. 7,335,395, filed on Jan. 13, 2003, entitled Methods ofUsing Pre-Formed Nanotubes to Make Carbon Nanotube Films, Layers,Fabrics, Ribbons, Elements, and Articles;

U.S. Pat. No. 7,259,410, filed on Feb. 11, 2004, entitled Devices HavingHorizontally-Disposed Nanofabric Articles and Methods of Making theSame;

U.S. Pat. No. 6,924,538, filed on Feb. 11, 2004, entitled Devices HavingVertically-Disposed Nanofabric Articles and Methods of Making Same;

U.S. Pat. No. 7,375,369, filed on Jun. 3, 2004, entitled Spin-CoatableLiquid for Formation of High Purity Nanotube Films;

U.S. Pat. No. 7,365,632, filed on Sep. 20, 2005, entitled RESISTIVEELEMENTS USING CARBON NANOTUBES; and

U.S. Pat. No. 7,567,414, filed on Nov. 2, 2005, entitled NANOTUBE ESDPROTECTIVE DEVICES AND CORRESPONDING NONVOLATILE AND VOLATILE NANOTUBESWITCHES.

This application is related to the following patent applications, whichare assigned to the assignee of the application, and are herebyincorporated by reference in their entirety.

U.S. patent application Ser. No. 10/341,005, filed on Jan. 13, 2003,entitled Methods of Making Carbon Nanotube Films, Layers, Fabrics,Ribbons, Elements, and Articles;

U.S. patent application Ser. No. 10/860,332, filed on Jun. 3, 2004,entitled HIGH PURITY NANOTUBE FABRICS AND FILMS;

U.S. patent application Ser. No. 11/304,315, filed on Dec. 15, 2005,entitled Aqueous Carbon Nanotube applicator Liquids and Methods forProducing Applicator Liquids Thereof;

U.S. patent application Ser. No. 12/533,687, filed on Jul. 31, 2009,entitled Anisotropic Nanotube Fabric Layers and Films and Methods ofForming Same; and

U.S. Patent App. No. 61/304,045, filed on Feb. 12, 2010, entitledMETHODS FOR CONTROLLING DENSITY, POROSITY, AND/OR GAP SIZE WITHINNANOTUBE FABRIC LAYERS AND FILMS.

BACKGROUND

Technical Field

The present disclosure relates generally to nanotube fabric layers andfilms and, more specifically, to methods for arranging nanotube elementswithin nanotube fabric layers and films via the application of adirectional force.

Discussion of Related Art

Any discussion of the related art throughout this specification shouldin no way be considered as an admission that such art is widely known orforms part of the common general knowledge in the field.

Nanotube fabric layers and films are used in a plurality of electronicstructures, and devices. For example, U.S. patent application Ser. No.11/835,856 to Bertin et al., incorporated herein by reference in itsentirety, teaches methods of using nanotube fabric layers to realizenonvolatile devices such as, but not limited to, block switches,programmable resistive elements, and programmable logic devices. U.S.Pat. No. 7,365,632 to Bertin et al., incorporated herein by reference,teaches the use of such fabric layers and films within the fabricationof thin film nanotube based resistors. U.S. patent application Ser. No.12/066,063 to Ward et al., incorporated herein by reference in itsentirety, teaches the use of such nanotube fabrics and films to formheat transfer elements within electronic devices and systems.

Through a variety of previously known techniques (described in moredetail within the incorporated references) nanotube elements can berendered conducting, non-conducting, or semi-conducting before or afterthe formation of a nanotube fabric layer or film, allowing such nanotubefabric layers and films to serve a plurality of functions within anelectronic device or system. Further, in some cases the electricalconductivity of a nanotube fabric layer or film can be adjusted betweentwo or more non-volatile states as taught in U.S. patent applicationSer. No. 11/280,786 to Bertin et al., incorporated herein by referencein its entirety, allowing for such nanotube fabric layers and films tobe used as memory or logic elements within an electronic system.

U.S. Pat. No. 7,334,395 to Ward et al., incorporated herein by referencein its entirety, teaches a plurality of methods for forming nanotubefabric layers and films on a substrate element using preformednanotubes. The methods include, but are not limited to, spin coating(wherein a solution of nanotubes is deposited on a substrate which isthen spun to evenly distribute said solution across the surface of saidsubstrate), spray coating (wherein a plurality of nanotube are suspendedwithin an aerosol solution which is then dispersed over a substrate),and dip coating (wherein a plurality of nanotubes are suspended in asolution and a substrate element is lowered into the solution and thenremoved). Further, U.S. Pat. No. 7,375,369 to Sen et al., incorporatedherein by reference in its entirety, and U.S. patent application Ser.No. 11/304,315 to Ghenciu et al., incorporated herein by reference inits entirety, teach nanotube solutions well suited for forming ananotube fabric layer over a substrate element via a spin coatingprocess.

While there exist a number of previously known techniques for moving andorienting individual nanotube elements—atomic force microscopy probes,for example, the use of which is well known by those skilled in the artfor adjusting the position of single nanotube elements in laboratoryexperiments and the like—there is a growing need within the currentstate of the art to arrange relatively large scale films and fabrics ofnanotube elements for larger scale, commercial applications. Forexample, as the physical dimensions of nanotube fabric based electronicdevices scale below twenty nanometers, there is a growing need todevelop denser nanotube fabrics. That is, to form nanotube fabrics insuch a way as to limit the size of—or, in some cases, substantiallyeliminate—gaps and voids between individual nanotube elements. Inanother example, within certain applications—such as, but not limitedto, nanotube fabric based field effect devices, nanotube fabric basedphotovoltaic devices, and nanotube fabric based sensors—there is a needfor nanotube fabric layers that exhibit relatively uniform physical andelectrical properties. Within such applications the orientation ofnanotube elements relative to each other within a film can significantlyaffect the overall electrical parameters of the film (such as, but notlimited to, charge mobility, sheet resistance, and capacitance).

Small scale nanotube arrangement techniques (such as, but not limitedto, atomic force microscopy) are typically limited to adjusting theposition of a very small number of nanotubes at a time, and thentypically only in the micron range. Further such laboratory basedmethods are not scalable or easily adapted to any large scale,commercial application. As such, such methods are not practical for thearrangement of nanotube elements in large scale films and fabrics.

A number of previously known techniques for orienting nanotube elementswithin a relatively large scale film involve subjecting a dispersion ofnanotube elements to an electrical or mechanical field as the dispersionis deposited over a substrate layer. For example, Ma et al. (“Alignmentand Dispersion of Functionalized Carbon Nanotubes in Polymer CompositesInduced by an Electric Field,” Carbon 46(4):706-710 (2008)) teaches analignment process for nanotube elements which includes applying anelectrical field to a quantity of functionalized multi-walled carbonnanotubes suspended in a polymeric composite. Under the effect of thefield, the functionalized nanotube will oriented themselves within thepolymeric composite into a substantially uniform orientation. In anotherexample, Merkulov et al. (“Alignment Mechanism of Carbon NanofibersProduced by Plasma-Enhanced Chemical Vapor Deposition,” Applied PhysicsLetters 79:2970 (2001)) teaches a method for directing the growth ofcarbon nanofibers by applying an electric field during a CVD growthprocess. In this way, nanotube growth will tend to follow the electricfield lines.

Some other previously known techniques for orienting nanotube elementswithin a film involve applying a mechanical force to compress verticallygrown (within respect to the plane of an underlying substrate) nanotubeelements into a film of substantially parallel nanotubes. For example,de Heer, et al. (Aligned Carbon Nanotube Films: Production and Opticaland Electronic Properties” Science 268(5212):845-847 (1995)) teaches amethod of using a Teflon or aluminum pad to compress a verticallyoriented distribution of nanotube elements into a film of essentiallyaligned nanotube elements. Similarly, Tawfick et al. (“FlexibleHigh-Conductivity Carbon-Nanotube Interconnects Made by Rolling andPrinting” Small (Weinheiman der Bergstrasse, Germany) (2009)) teaches amethod of using a roller element to pack down a distribution ofvertically grown nanotube elements into a substantially alignedhorizontal film.

While these related techniques do not require a mobilizing fluid vehicle(as in the methods taught by Ma and Merkulov), they do require adistribution of vertically grown nanotubes. The fabrication and use ofsuch vertical films grown in situ can be limiting within certainapplications. For example, the growth of vertical nanotube filmstypically requires special operation conditions (such as, but notlimited to, high temperatures, certain regents, and high gas pressures),which can be undesirable or otherwise inconvenient within certainsemiconductor manufacturing operations. Such conditions may beincompatible with certain substrate materials, for example. Further, thecatalysts used to grow nanotubes are typically metals or metalloids,materials which can be difficult to remove within high purityapplications. Further, in situ growth of films limit the ability to formblends of nanotube formulations—for example, combinations ofsemiconducting and metallic nanotubes, single walled and multi wallednanotubes, or nanotubes mixed with other materials like buckyballs,silica, or other material particles. Further still, the roughness ofvertically grown films is dictated by the density and uniformity of thevertical tubes as grown without additional liquid processing to enhancetube association. Such limitations within the growth of verticalnanotube films reduce their effectiveness and limit their applicabilityin large scale, commercial applications.

While these and other similar previously known methods provide somemeans of aligning or otherwise orienting nanotube elements, they arelimited in that they require either wet suspensions of nanotube elementsor nanotube elements grown in vertical orientations. Within manyapplications, these limitations will substantially limit theeffectiveness of these techniques in commercial applications. Further,these previously known techniques will tend to limit the orientation ofthe aligned nanotube elements along a single direction. As such, thereis a need for an efficient and relatively uncomplicated method ofarranging nanotube elements within a dry nanotube fabric (for example, ananotube fabric formed by spin coating a nanotube application solutionover a substrate). Further, there is a need for a method of arrangingnanotube elements within a nanotube fabric according to a preselectedorientation (which may include nanotube arrangement along multipledirections).

SUMMARY

The current disclosure relates to methods for arranging nanotubeelements within nanotube fabric layers and films via the application ofa directional force.

In particular, the present disclosure provides a method for arrangingnanoscopic elements within a network. The method comprises firstproviding a network of nanoscopic elements disposed over a materiallayer. The method further comprises applying a directional force to atleast a portion of the network of nanoscopic elements to arrange atleast a portion of the nanoscopic elements into an ordered network.

According to one aspect of the present disclosure a networks ofnanoscopic elements include nanotube fabrics.

According to another aspect of the present disclosure nanoscopicelements include carbon nanotubes, nanowires, and mixtures thereof.

According to another aspect of the present disclosure a lubricatingmedium is deposited over a network of nanoscopic elements prior to theapplication of a directional force.

According to another aspect of the present disclosure, a method forforming a nanotube fabric layer comprises forming an unordered nanotubefabric layer over a material surface and applying a directional forceover said unordered nanotube fabric layer to render at least a portionof said unordered nanotube fabric layer into an ordered network ofnanotube elements.

According to another aspect of the present disclosure a punctureresistant material comprises a supporting structure and an orderednanotube fabric element, said ordered nanotube fabric element comprisingat least one ordered nanotube fabric layer, wherein said orderednanotube fabric element is affixed to said supporting structure suchthat said ordered nanotube fabric element covers to a least a portion ofsaid supporting structure material.

According to another aspect of the present disclosure an orderednanotube fabric layer comprises a network of nanotube elements whereingroupings of said nanotube elements are arranged in a substantiallyuniform manner such that said groupings of nanotube elements arepositioned essentially parallel to adjacent nanotube elements.

According to another aspect of the present disclosure an orderednanotube fabric layer comprises a network of nanotube elements denselypacked together, substantially minimizing gaps within said orderednanotube fabric layer.

According to another aspect of the present disclosure an orderednanotube fabric layer comprises a network of nanotube elements whereinthe individual nanotube elements are separated from adjacent nanotubeelements by gaps on the order of 1-2 nm.

According to another aspect of the present disclosure an orderednanotube fabric layer comprises a network of nanotube elements whereinthe individual nanotube elements are separated from adjacent nanotubeelements by gaps on the order of 10 nm.

According to another aspect of the present disclosure an orderednanotube fabric layer comprises a network of nanotube elements whereinthe individual nanotube elements are separated from adjacent nanotubeelements by gaps on the order of 50 nm.

According to another aspect of the present disclosure an orderednanotube fabric layer comprises a network of functionalized nanotubeelements, said functionalized elements coated with moieties such as toelectrically insulate the sidewalls of individual nanotube elements fromthe sidewalls of adjacent nanotube elements.

According to another aspect of the present disclosure a nanotube fabriclayer comprises an ordered network of nanotube elements, whereinsubstantially all of the nanotube elements are parallel to and incontact with a plurality of other nanotube elements along the long axisof the nanotube elements.

According to another aspect of the present disclosure a nanotube fabriclayer comprises an ordered network of nanotube elements, wherein thenanotube fabric is impermeable to micron-sized particles.

According to another aspect of the present disclosure a nanotube fabriclayer comprises an ordered network of nanotube elements, wherein thenanotube fabric is impermeable to nano-sized particles.

According to another aspect of the present disclosure an unorderednanotube fabric layer is formed via at least one spin coating operation.

Under another aspect of the present disclosure an unordered nanotubefabric layer is formed via at least one spray coating operation.

Under another aspect of the present disclosure an unordered nanotubefabric layer is formed via at least one dip coating operation.

Under another aspect of the present disclosure an unordered nanotubefabric layer is formed via a silk screen printing process.

Under another aspect of the present disclosure an unordered nanotubefabric layer is formed via a gravure or other large format film printingprocess.

Under another aspect of the present disclosure a rolling force isapplied to an unordered nanotube fabric layer by rolling a cylindricalelement over said unordered nanotube fabric layer.

Under another aspect of the present disclosure a rubbing force isapplied to an unordered nanotube fabric layer by sliding the unorderednanotube fabric layer over a material surface.

Under another aspect of the present disclosure a directional force isapplied to an unordered nanotube fabric layer by positioning a pliantfilm onto the CNT surface and then impinging a pressurized gas, a jet offrozen gas, or a jet of other particles or liquids over the surface ofthe intervening pliant layer

Under another aspect of the present disclosure a polishing force isapplied to an unordered nanotube fabric layer by passing a polishingmaterial over the surface of the unordered nanotube fabric layer.

Under another aspect of the present disclosure a polishing force isapplied to an unordered nanotube fabric layer by applying a rotatingpolishing material to the surface of the unordered nanotube fabriclayer.

Other features and advantages of the present invention will becomeapparent from the following description of the invention which isprovided below in relation to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is force diagram illustrating the translation of a directionalforce over a nanotube fabric;

FIG. 2A is an illustration of an exemplary nanotube fabric layercomprised of a substantially unordered network of nanotube elements;

FIG. 2B is an SEM image of an exemplary nanotube fabric layer comprisedof a substantially unordered network of nanotube elements;

FIG. 2C is an illustration of an exemplary nanotube fabric layercomprised of a highly ordered network of nanotube elements;

FIG. 2D is an SEM image of an exemplary nanotube fabric layer comprisedof a highly ordered network of nanotube elements;

FIGS. 3A-3F are perspective drawings illustrating an exemplary processaccording to the methods of the present disclosure for rendering asubstantially unordered nanotube fabric layer into an ordered network ofnanotube elements via a directional force;

FIG. 4 is a process diagram illustrating a method of rendering asubstantially unordered nanotube fabric layer into an ordered network ofnanotube elements through the application of a linear directional force;

FIG. 5 is a process diagram illustrating a method of rendering asubstantially unordered nanotube fabric layer into an ordered network ofnanotube elements through the application of two linear directionalforces, each force applied separately and in different directions;

FIG. 6 is a process diagram illustrating a method of rendering asubstantially unordered nanotube fabric layer into an ordered network ofnanotube elements through the application of a rotational directionalforce;

FIG. 7A is a perspective drawing depicting an exemplary rollingapparatus suitable for applying a directional force over a nanotubefabric layer according to the methods of the present disclosure;

FIG. 7B is a diagram illustrating the operation of the exemplary rollingapparatus depicted in FIG. 7A;

FIG. 8A is a perspective drawing depicting an exemplary rubbingapparatus suitable for applying a directional force over a nanotubefabric layer according to the methods of the present disclosure;

FIG. 8B is a diagram illustrating the operation of the exemplary rubbingapparatus depicted in FIG. 8A;

FIG. 9A is a perspective drawing depicting an exemplary rubbingapparatus suitable for applying a directional force in an arc over ananotube fabric layer according to the methods of the presentdisclosure;

FIG. 9B is a diagram illustrating the operation of the exemplary rubbingapparatus depicted in FIG. 9A;

FIG. 10A is a perspective drawing depicting an exemplary polishingapparatus suitable for applying a linear directional force over ananotube fabric layer according to the methods of the presentdisclosure;

FIG. 10B is a diagram illustrating the operation of the exemplarypolishing apparatus depicted in FIG. 10A;

FIG. 11A is a perspective drawing depicting an exemplary polishingapparatus suitable for applying a rotational directional force over ananotube fabric layer according to the methods of the presentdisclosure;

FIG. 11B is a diagram illustrating the operation of the exemplarypolishing apparatus depicted in FIG. 11A;

FIG. 12A is a perspective drawing depicting an exemplary cryokineticimpingement apparatus suitable for applying a directional force over ananotube fabric layer according to the methods of the presentdisclosure;

FIG. 12B is a diagram illustrating the operation of the exemplarycryokinetic impingement apparatus depicted in FIG. 12A;

FIG. 13A is a perspective drawing depicting an exemplary roll-to-rollpolishing apparatus suitable for applying a linear directional forceover a nanotube fabric layer according to the methods of the presentdisclosure;

FIG. 13B is a diagram illustrating the operation of the exemplaryroll-to-roll polishing apparatus depicted in FIG. 13A;

FIGS. 14A-14B are cross sectional images of a three-layer structureincluding a substantially unordered nanotube fabric layer;

FIGS. 15A-15B are cross sectional images of a three-layer structureincluding an ordered nanotube fabric layer;

FIG. 16 is a diagram illustrating an apparatus used to determine thefrictional observed over a partially ordered nanotube fabric layer;

FIG. 17 is a plot of the frictional forces observed with the apparatusof FIG. 16 over a partially ordered nanotube fabric layer;

FIG. 18 is an illustration drawing depicting a multi-layer nanotubefabric element comprised of multiple layers of ordered nanotube elementswherein each layer comprises nanotube elements oriented in a directiondifferent from those in adjacent layers;

FIGS. 19A-19C are SEM images (at different magnifications) of anexemplary nanotube fabric layer comprising a network of nanotubeelements rendered into an ordered arrangement through the application ofa directional rolling force;

FIGS. 20A-20C are SEM images (at different magnifications) of anexemplary nanotube fabric layer comprising regions of nanotube elementsrendered into a partially ordered arrangement after fifteen rubbingpasses over a TEFLON or polytetrafluoroethylene film;

FIGS. 21A-21C are SEM images (at different magnifications) of anexemplary nanotube fabric layer comprising a network of nanotubeelements rendered into an ordered arrangement after twenty five rubbingpasses over a TEFLON or polytetrafluoroethylene film;

FIGS. 22A-22C are SEM images (at different magnifications) of anexemplary nanotube fabric layer comprising a network of nanotubeelements rendered into an ordered arrangement after two hundred andfifty rubbing passes over a silicon wafer;

FIGS. 23A-23C are SEM images (at different magnifications) of anexemplary nanotube fabric layer comprising a network of nanotubeelements rendered into an ordered arrangement after one hundred passesof a wool rubbing pad swept across the nanotube fabric layer in anarcing motion;

FIGS. 24A-24C are SEM images (at different magnifications) of anexemplary nanotube fabric layer comprising a network of nanotubeelements rendered into an ordered arrangement after fifty passes of avelour polishing roller swept across the nanotube fabric layer in anlinear motion;

FIGS. 25A-25C are SEM images (at different magnifications) of anexemplary nanotube fabric layer comprising a network of nanotubeelements rendered into an ordered arrangement after the application of arotational directional force over the nanotube fabric layer via arotating wool polishing pad rotated at sixty rpm for ninety seconds;

FIGS. 26A-26C are SEM images (at different magnifications) of anexemplary nanotube fabric layer comprising a network of unorderednanotube elements;

FIGS. 27A-27C are SEM images (at different magnifications) of theexemplary nanotube fabric layer of FIGS. 26A-26C after being renderedinto a network of nanotube elements by sliding a weighted CMP pad alongthe length of the nanotube fabric layer 20 times;

FIGS. 28A-28D are SEM images (at different magnifications) detailing therendering of an exemplary nanotube fabric layer into an ordered statevia a cryokinetic impingement operation;

FIGS. 29A-29C are SEM images detailing the rendering of an exemplarynanotube fabric layer deposited over a 1018 low carbon steel substrateinto an ordered state via a rubbing operation;

FIGS. 30A-30D are SEM images (at different magnifications) detailing therendering of an exemplary nanotube fabric layer into an ordered statevia piezoelectric rubbing operation;

FIGS. 31A-31C are SEM images (at different magnifications) detailing therendering of an exemplary nanotube fabric layer deposited over apolyethylene terephthalate (PET) substrate into an ordered state via arubbing operation;

FIGS. 32A-32D are SEM images (at different magnifications) detailing therendering of an exemplary nanotube fabric layer into an ordered statevia a high pressure air flow polishing operation;

FIGS. 33A-33B are SEM images detailing the rendering of an exemplarynanotube fabric layer deposited over a 2024 aluminum alloy substrateinto an ordered state via a rubbing operation;

FIGS. 34A-34C are SEM images detailing the rendering of an exemplarynanotube fabric layer deposited over a titanium nitride (TiN) substrateinto an ordered state via a rubbing operation performed using a chemicalmechanical polishing (CMP) machine;

FIG. 35 is an AFM image detailing the rendering of an exemplary nanotubefabric layer into an ordered state via the use of an electronicallycontrolled linear actuator to provide a rubbing force with a strokelength of 1 mm;

FIG. 36 is an AFM image detailing the rendering of an exemplary nanotubefabric layer into an ordered state via the use of an electronicallycontrolled linear actuator to provide a rubbing force with a strokelength of 0.1 mm;

FIG. 37 is an AFM image detailing the rendering of an exemplary nanotubefabric layer into an ordered state via the use of an electronicallycontrolled linear actuator to provide a rubbing force with a strokelength of 0.05 mm;

FIG. 38 is an AFM image detailing the rendering of an exemplary nanotubefabric layer into an ordered state via the use of an electronicallycontrolled linear actuator to provide a rubbing force with a strokelength of 0.01 mm;

FIGS. 39A-39D are SEM images detailing the rendering of an exemplarynanotube fabric layer coated with a layer of silicon nanowires into anordered state via the use of a rayon rubbing pad.

DETAILED DESCRIPTION

The present disclosure teaches methods to arrange nanotube elementswithin nanotube fabric layers and films through the application of adirectional force applied over such layers and films. These approachescan be employed to render regions, within a deposited nanotube fabriclayer, into one or more networks of substantially ordered nanotubeelements—that is, regions wherein the nanotube elements are oriented ina substantially uniform arrangement such that they group together alongtheir sidewalls. In this manner, for example, nanotube fabrics may becreated which are highly dense. In certain applications, such orderednanotube fabric layers would be essentially free of gaps and voidsbetween nanotube elements. Or, in another example, ordered nanotubefabrics may be created which are essentially free of gaps and voidsgreater than a certain dimension. Further, in another example, suchmethods may be used to realize nanotube fabrics wherein the number ofgaps and voids within the fabric is significantly reduced. In stillanother example, an ordered nanotube fabric layer, arranged according tothe methods of the present disclosure, includes a plurality of nanotubeelements oriented in substantially the same direction.

It should be noted that within the present disclosure the term “network”is used to describe an arrangement of nanotube elements dispersed overthe surface of a substrate. In certain applications networks of nanotubeelements are relatively dense, with nanotube elements packed tightlytogether and, in some cases, entwined with adjacent nanotube elements.In other applications network of nanotube elements are relativelysparse, with gaps and spaces between individual nanotube elements.Within certain applications, individual nanotube elements with sparsenetworks might be separated by gaps on the order of 1-2 nm. Within otherapplications such gaps might be on the order of 10 nm. Within stillother applications such gaps might be on the order of 50 nm.

A fabric of nanotubes as referred to herein for the present disclosureincludes a layer of multiple, interconnected carbon nanotubes. A fabricof nanotubes (or nanofabric), in the present disclosure, e.g., anon-woven carbon nanotube (CNT) fabric, may, for example, have astructure of multiple entangled nanotubes that are irregularly arrangedrelative to one another. Alternatively, or in addition, for example, thefabric of nanotubes for the present disclosure may possess some degreeof positional regularity of the nanotubes, e.g., some degree ofparallelism along their long axes. Such positional regularity may befound, for example, on a relatively small scale wherein flat arrays ofnanotubes are arranged together along their long axes in rafts on theorder of one nanotube long and ten to twenty nanotubes wide. In otherexamples, such positional regularity maybe found on a larger scale, withregions of ordered nanotubes, in some cases, extended over substantiallythe entire fabric layer. Such larger scale positional regularity is ofparticular interest to the present disclosure.

The fabrics of nanotubes retain desirable physical properties of thenanotubes from which they are formed. For example, in some electricalapplications the fabric preferably has a sufficient amount of nanotubesin contact so that at least one ohmic (metallic) or semi-conductivepathway exists from a given point within the fabric to another pointwithin the fabric. Single walled nanotubes may typically have a diameterof about 1-3 nm, and multi walled nanotubes may typically have adiameter of about 3-30 nm. Nanotubes may have lengths ranging from about0.2 microns to about 200 microns, for example. The nanotubes may curveand occasionally cross one another. Gaps in the fabric, i.e., betweennanotubes either laterally or vertically, may exist. Such fabrics mayinclude single-walled nanotubes, multi-walled nanotubes, or both. Thefabric may have small areas of discontinuity with no tubes present. Thefabric may be prepared as a layer or as multiple fabric layers, oneformed over another. The thickness of the fabric can be chosen as thinas substantially a monolayer of nanotubes or can be chosen much thicker,e.g., tens of nanometers to hundreds of microns in thickness. Theporosity of the fabrics can vary from low density fabrics with highporosity to high density fabrics with low porosity. Such fabrics can beprepared by growing nanotubes using chemical vapor deposition (CVD)processes in conjunction with various catalysts, for example. Othermethods for generating such fabrics may involve using spin-coatingtechniques and spray-coating techniques with preformed nanotubessuspended in a suitable solvent, silk screen printing, gravure printing,and electrostatic spray coating. Nanoparticles of other materials can bemixed with suspensions of nanotubes in such solvents and deposited byspin coating and spray coating to form fabrics with nanoparticlesdispersed among the nanotubes. Such exemplary methods are described inmore detail in the related art cited in the Background section of thisdisclosure.

It should be noted that while much of the present disclosure discussesmethods for the arrangement of nanotube elements within a nanotubefabric, the methods of the present disclosure are not limited in thisregard. Indeed, the methods of the present disclosure can be used toarrange high aspect ratio nanoscopic elements (that is, nanoscopic “tubelike” structures with length to width ratios on the order of 4 to 1wherein at least one of those dimensions—length or width—is less than100 nm) within a plurality of fabrics or networks. Such nanoscopicelements include, but are not limited to, single wall nanotubes,multiwalled nanotubes, nanowires, and mixtures thereof. Nanowires asmentioned herein is meant to mean single nanowires, aggregates ofnon-woven nanowires, nanoclusters, nanowires entangled with nanotubescomprising a nanofabric, mattes of nanowires, etc. Examples of nanowire(nanorod) materials are alumina, bismuth, cadmium, selenide, galliumnitride, gold, gallium phosphide, germanium, silicon, indium phosphide,magnesium oxide, manganese oxide, nickel, palladium, silicon carbide,titanium, zinc oxide and additional mixed nanowires such as silicongermanium or other types which are coated. Further, within the presentdisclosure networks of nanoscopic elements are described as arrangementsof such freely formed and deposited nanoscopic elements in asubstantially planer configuration. Exemplary networks of nanoscopicelements include, but are not limited to, nanotube fabric layers asdescribed within the present disclosure and arrangements of nanowiresdispersed over a material surface.

As described within U.S. Pat. No. 7,375,369 to Sen et al. and U.S.patent application Ser. No. 11/304,315 to Ghenciu et al., bothincorporated herein by reference in their entirety, nanotube fabrics andfilms can be formed by applying a nanotube application solution (forexample, but not limited to, a plurality of nanotube elements suspendedwithin an aqueous solution) over a substrate element. A spin coatingprocess, for example, can be used to evenly distribute the nanotubeelements over the substrate element, creating a substantially uniformlayer of nanotube elements. In other cases, other processes (such as,but not limited to, spray coating processes, dip coating processes, silkscreen printing processes, and gravure printing processes) can be usedto apply and distribute the nanotube elements over the substrateelement. In other cases, CVD growth of nanotubes on a material surfacemay be used to realize an unordered nanotube fabric layer. Further, U.S.Patent App. No. 61/304,045 to Sen et al., incorporated herein byreference in its entirety, teaches methods of adjusting certainparameters (for example, the nanotube density or the concentrations ofcertain ionic species) within nanotube application solutions to eitherpromote or discourage rafting—that is, the tendency for nanotubeelements to group together along their sidewalls and form dense,raft-like structures—within a nanotube fabric layer formed with such asolution. By increasing the incidence of rafting within nanotube fabriclayers, the density of such fabric layers can be increased, reducingboth the number and size of voids and gaps within such fabric layers.

It should be noted that nanotube elements used and referenced within theembodiments of the present disclosure may be single-walled nanotubes,multi-walled nanotubes, or mixtures thereof and may be of varyinglengths. Further, the nanotubes may be conductive, semiconductive, orcombinations thereof. Further, the nanotubes may be functionalized (forexample, by oxidation with nitric acid resulting in alcohol, aldehydic,ketonic, or carboxylic moieties attached to the nanotubes), or they maybe non-functionalized.

It should be noted that the methods of the present disclosure are wellsuited for arranging functionalized nanotube elements within a nanotubefabric layer. Nanotube elements may be functionalized for a plurality ofreasons. For example, certain moieties may be formed on the sidewalls ofnanotube elements to add in the dispersion of those elements within anapplication solution. In another example, certain moieties formed on thesidewalls of nanotube elements can aid in the efficient formation of ananotube fabric. In a further example, nanotube elements can befunctionalized with certain moieties such as to electrically insulatethe sidewalls of the nanotube elements. Nanotube elements can befunctionalized by attaching organic, silica, or metallic moieties (orsome combination thereof) to the sidewalls of the nanotube elements.Such moieties can interact with nanotube elements covalently or remainaffixed through π-π bonding.

The reduction or substantial elimination of gaps and voids within ananotube fabric layer is particularly useful for devices with extremelysmall circuit sizes in which a uniform dispersion of nanotubes isdesired. For example, when a fabric with very few—or only verysmall—gaps and voids is patterned and etched, the remaining nanotubearticle is effectively assured of containing nanotubes as opposed tolacking nanotubes as a result of a large void in the fabric. As thefeature sizes decrease along with currently practiced lithographytechniques, minimizing gaps and voids within nanotube fabric layersbecomes more important to ensure a higher yield of functional circuitelements as the fabric is being etched.

For example, within some applications advancing lithography techniquesmay determine a minimum feature size (e.g., on the order of 20 nm).Voids and gaps within a nanotube fabric layer larger than some fractionof such a feature size (e.g., larger than about 10 nm) may result innonfunctioning or ineffective circuit elements. By minimizing—orotherwise substantially eliminating—gaps and voids within a nanotubefabric layer, the incidence of such nonfunctioning or ineffectivecircuit elements can be significantly reduced.

In some applications by minimizing or substantially eliminating gaps andvoids within a nanotube fabric layer, the density of an array ofnanotube switching devices fabricated from that layer may be increased.U.S. patent application Ser. No. 11/280,786 to Bertin et al.,incorporated herein by reference in its entirety, teaches a nonvolatiletwo terminal nanotube switch structure having (in at least oneembodiment) a nanotube fabric article deposited between two electricallyisolated electrode elements. As Bertin teaches, by placing differentvoltages across said electrode elements, the resistive state of thenanotube fabric article can be switched between a plurality ofnonvolatile states. That is, in some embodiments the nanotube fabricarticle can be repeatedly switched between a relatively high resistivestate (resulting in, essentially, an open circuit between the twoelectrode elements) and a relatively low resistive state (resulting in,essentially, a short circuit between the two electrode elements).

In other applications, relatively low density ordered nanotubefabrics—in some cases, on the order of a single nanotube thick—can behighly beneficial. Certain logic applications, for example, make use ofrelatively thin nanotube fabric layers as charge conducting planes. Suchapplications require that conduction paths through the nanotube fabriclayer be substantially uniform. Within such applications, a thin and/orlow density nanotube fabric layer can be arranged into an orderednetwork of nanotube elements oriented in a uniform direction, whereinthe individual nanotube elements tend not to overlap or contact adjacentnanotube elements.

The fabrication of an array of such nanotube switching devices caninclude patterning of a nanotube fabric layer to realize a plurality ofthese nanotube fabric articles. The number and the size of the gaps andvoids within a nanotube fabric layer can limit the feature size to whichthese nanotube fabric articles within such an array can be patterned.For example, within a nanotube switching device array wherein theindividual nanotube switching devices are on the order of 20 nm square(that is, the nanotube fabric article within each device is essentially20 nm by 20 nm), gaps within the nanotube fabric layer larger than about10 nm, for example, may result in nonfunctioning or ineffective nanotubeswitching devices. For example, a typical unordered nanotube fabriclayer may exhibit gaps over approximately 25% of its surface, and atypical ordered nanotube fabric layer may exhibit gaps overapproximately 2% of its surface. By minimizing the number of gaps withinthe fabric layer—or limiting the size of these gaps—prior to theformation of the array of nanotube switching elements, the incidence ofthese nonfunctioning or ineffective nanotube switching devices can besignificantly reduced or—in some applications—essentially eliminated.

Within the methods of the present disclosure, nanotube fabrics aretypically formed over other material layers (through, for example, oneor more spin coating operations). In some applications this materiallayer may be a silicon wafer. In other applications, this material layermay be a conductive material, such as, but not limited to, tungsten,aluminum, copper, nickel, palladium, titanium nitride, and tungstennitride. In still other applications, this material layer may be asemiconducting material such as, but not limited to, silicon and galliumarsenide. In other applications, this material layer may be a dielectricmaterial such as, but not limited to, silicon oxide and aluminum oxide.In still other applications, this material layer may be an organicsemiconducting material such as, but not limited to, polyfluorenepolythiophenes, polyacetylenes, polypyrroles, polyanilines,poly(p-phenylene sulfide), and poly(p-phenylene vinylene)s.

In some applications this material layer may be formed of a rigidmaterial, such as, but not limited to, metal (e.g., steel or aluminum),ceramic, or glass. In other applications it may be formed of a flexiblematerial such as a plastic film or sheet—e.g., polyethyleneterephthalate (PET), polymethylmethacrylate, polyamides, polysulfones,and polycyclic olefins. In other applications a desired interfacematerial (such as, but not limited to, silicon oxide) may be formed overa rigid material (such as, but not limited to, steel) to form a rigidstructural composite which provides a substrate with the desiredinterface properties of a first material with the structural propertiesof a second material.

Dependant on the needs of an application, such material layers may beformed from materials such as, but not limited to, elemental silicon,silicon oxide, silicon nitride, silicon carbides, PTFE, organic polymer(including, but not limited to, polyesters, pvc, styrenes, polyvinylalcohol, and polyvinyl acetate), hydrocarbon polymers (including, butnot limited to, poly ethylene, polly propylene, and polycellosics),inorganic backbone polymers (including, but not limited to, siloxanes,polyphophazenes), boron nitride, gallium arsenide, group III/Vcompounds, group III/V compounds, wood, metals—including metal alloysand metal oxides (including, but not limited to, steel, aluminum,nickel, iron, manganese, titanium, copper, zinc, and tin), ceramics(including, but not limited to, aluminum oxide, cerium oxide, magnesiumoxide, titanium oxide, tin oxides, zinc oxides), and glass (including,but not limited to, silicate glass, boron silicate glass, and sodiumsilicate glass).

In certain embodiments of the present disclosure, nanotube fabric layers(rendered into ordered networks of nanotube elements by the methods ofthe present disclosure) may be separated from a material layer torealize standalone nanotube fabric layers.

In other applications an ordered nanotube fabric layer—wherein, forexample, the majority of nanotube elements are oriented in substantiallythe same direction—can be used to provide a nanotube fabric whichexhibits a relatively uniform electrical or physical properties (suchas, but not limited to, sheet resistance, uniformity of charge carriers,and heat transfer). Such ordered nanotube fabric can be useful in thefabrication of electronic devices and components, such as, but notlimited to, non-volatile switching elements, nanotube fabric based logicdevices, and heat transfer structures.

In other applications an ordered nanotube fabric layer substantiallyfree of gaps and voids can be used to form a protective barrier layerover or around an adjacent material layer. For example, a thin nanotubefabric layer comprised of an ordered network of nanotube elements may beformed over a thicker unordered nanotube fabric layer. In this way, thethin ordered nanotube fabric layer—essentially free of gaps andvoids—provides a barrier layer between the thicker unordered nanotubelayer and any material layer (e.g., a conductive contact layer such astungsten) deposited over the two nanotube fabric layers in subsequentprocess steps. In another example, an ordered nanotube fabric layer—withminimal gaps and voids—can be used to protect an underlying materiallayer from external contaminants (e.g., water, catalytic metals, andamorphous carbon). Such an ordered nanotube fabric layer may be used,for example, to form a substantially hydrophobic protective layer forOLED (organic light emitting diode) displays or photovoltaic cells. Inanother example, such ordered nanotube fabric layers may be used torealize protective packaging for shipping materials. In still anotherexample such an ordered nanotube fabric layer may be used to form ananticorrosion layer over the body panel of a vehicle.

In other applications an ordered nanotube fabric layer can be used toprovide a low or otherwise reduced frictional coating over a materiallayer. In certain applications an ordered nanotube fabric layer (whereinthe nanotube elements have been oriented in a substantially uniformdirection via the methods of the present disclosure) will exhibit a lowcoefficient of friction. Such ordered nanotube fabric layers can be usedto reduce the friction between moving pieces within mechanical systems(such as, but not limited to, engine cylinders, pistons, and movingelements within MEMS devices). Such ordered nanotube fabric layers canalso be used to provide low friction coatings over certain objects (suchas, but not limited to, cookware and skis).

FIG. 1 is a force diagram illustrating the translation of an exemplarydirectional force over a nanotube fabric 120. As depicted in FIG. 1, anapplied force 130 is delivered to the surface of a nanotube fabric 120at angle θ (within this example, the nanotube fabric 120 has been formedover a material layer 110). The vertical 130 b and horizontal 130 acomponents of this applied force 130 act upon nanotube fabric layer 120as the applied force 130 is moved across the nanotube fabric layer 120along direction 150. The horizontal component 130 a of applied force 130works across the nanotube fabric 120 within the plane of the nanotubefabric 120, creating a directional force across the nanotube fabriclayer. In some embodiments of the present disclosure—those embodimentswherein the horizontal component 130 a of the applied force 130 isessentially a frictional force—the magnitude vertical component 130 b ofthe applied force 130 can be used to modulate the magnitude horizontalcomponent, and thus, the magnitude of the directional force. As will beshown within the present disclosure, the translation of such adirectional force across a nanotube fabric will tend to arrange thenanotube elements within the nanotube fabric into an ordered networkoriented substantially along the path of the directional force. The workdone by translating a directional force across a nanotube fabric impartsenergy into the nanotube fabric, which is used to arrange the individualnanotube elements. In certain embodiments of the present disclosure,multiple iterations of a directional force (that is, multiple passes ofa directional force across the nanotube fabric) will impart such energyas to render more and more of the nanotube elements into an orderedarrangement with each successive pass.

The present disclosure teaches multiple apparatus for translating adirectional force over a nanotube fabric in one or more directions. Insome embodiments a directional force is applied once over a nanotubefabric. In other embodiments a directional force is applied multipletimes, with each iteration of the applied directional force followingsubstantially the same path (either moving back and forth over thispath, or returning to a starting position for each iteration such thatthe directional force is only applied in a single direction) across thenanotube fabric. In some embodiments a substantially uniform directionalforce (in terms of magnitude and direction) will be applied over anentire nanotube fabric in order to orient the nanotube elements withinthe fabric along a single direction. In other embodiments the magnitudeand direction of a directional force will be selected for differentregions of a nanotube fabric such as to orient the nanotube elementswithin a fabric into a preselected pattern. It should be noted that, inthe preferred embodiment of the present disclosure, an applied force(130 in FIG. 1) is applied at a non-perpendicular angle (that is θ isnot equal to 90 degrees) and applied for multiple iterations. Further,it is preferable to use more iterations than fewer.

By applying a directional force over an essentially unordered network ofnanotube elements, the nanotube elements may be rendered into anessentially ordered network, significantly limiting—or, in someapplications, substantially eliminating—the number of gaps and voidsbetween nanotube elements and orienting the nanotube elements into oneor more substantially uniform directions. It should be noted that whilethe diagram of FIG. 1 depicts the application of a linear directionalforce applied directly to a nanotube fabric, the methods of the presentdisclosure are not limited in this regard. According to the methods ofthe present disclosure this directional force can be directly applied(wherein, for example, an apparatus applies a directional force directlyto nanotube elements within a fabric layer) or transferred (wherein, forexample, a directional force is applied through an another material).Further, in certain applications a directional force applied directly toone or more nanotube elements in a nanotube fabric layer can betransferred through those elements to other nanotube elements within thefabric layer. Exemplary directional forces include, but are not limitedto, rolling, rubbing, polishing, and cryokinetic impingement. Suchforces can be applied linearly (that is, across the surface of a fabriclayer along a straight line), in an arc, or rotationally.

As previously discussed, it should be noted that a directional force asdescribed above can be applied over a freely formed, fixed nanotubefabric. That is, over a substantially dry, fully formed nanotube fabric(that is, a nanotube fabric substantially free of any suspension mediumwhich allows the nanotubes a range of motion) and formed from aplurality of free nanotube elements. That is, nanotube elements producedand harvested in an independent operation, such that the nanotubeelements may be purified, sorted, and selected as desired by the needsof a specific application. In certain applications, this will allow themethod for arranging nanotube elements within a nanotube fabric toessentially decouple from the method of forming that fabric. In thisway, the methods of the present disclosure can be used to arrangenanotube fabric layers formed through a plurality of deposition andformation techniques (such as, but not limited to, spin coating, spraycoating, dip coating, silk screen printing, and gravure printing) at adesired or preselected density, geometry, and configuration.

Further, the methods of the present disclosure do not require verticallygrown films. As previously discussed, such vertically grown films (aswell as the previously known methods for flatting them into asubstantially aligned arrangement) can be limiting in many applications.For example, the previously known methods for flattening vertical filmsare limited in that they cannot rearrange nanotube elements once theyhave been flattened. As will be shown, in certain embodiments themethods of the present disclosure can be used to arrange a freely formedfixed nanotube fabric multiple times and in multiple directions.Vertically grown films can also be limited in applications where ananotube film is formed over a non-flat material layer. Growing from adeposited catalyst layer, vertically grown nanotubes in suchapplications will tend to follow the topography of an underlyingmaterial layer. In such applications, however, a freely formed, fixednanotube fabric can deposited in relatively thick layers (via, forexample, a spin coating operation) such as to provide a substantiallyplanar top surface. The methods of the present disclosure can then beused to arrange part or all of this freely formed, fixed nanotube fabricinto a dense, ordered network of nanotube elements.

It should also be noted that while vertically grown nanotube films arelimited in the type and quality of nanotube elements grown, a freelyformed fixed nanotube fabric layer can be comprised of independentlyselected (and in some cases, purified and/or functionalized) nanotubeelements. As such, the methods of the present disclosure may be used toarrange nanotube elements within a nanotube fabric formed with apreselected configuration. For example, the methods of the presentdisclosure can be used to arrange nanotube elements within nanotubefabrics made up of metallic nanotubes, semiconducting nanotubes, or somecombination thereof. Similarly, the methods of the present disclosurecan be used to arrange nanotube elements within nanotube fabrics made upof single walled nanotubes, multi walled nanotubes, or some combinationthereof. Further, the methods of the present disclosure can be used toarrange nanotube elements within nanotube fabrics which are compositesof nanotubes and other materials (such as, but not limited to,buckyballs, silica particles, amorphous carbon, silver nanotubes,quantum dots, colloidal silver, and monodisperse polystyrene beads).Further still, the methods of the present disclosure can be used toarrange nanotube elements within nanotube fabrics made up of nanotubeelements which have been functionalized to have specific electricalproperties or to react with certain physical or chemical conditions in adesired way.

In some embodiments of the present disclosure a directional force isapplied over a nanotube fabric by moving a material surface across thenanotube fabric. In other embodiments a directional force is applied bymoving a nanotube fabric (affixed to some substrate element, forexample) across a fixed material surface. Further, the methods of thepresent disclosure can be used to arrange nanotube fabrics that includemixtures of nanotube elements and other materials. Such materials caninclude, but are not limited to, buckyballs, amorphous carbon, silvernanotubes, quantum dots (on the order of 2-10 nm), colloidal silver (onthe order of 20 nm), monodisperse polystyrene beads (on the order of 200nm), and silica particles (up to 600 nm). The methods of the presentdisclosure can be used to arrange nanotube elements within nanotubefabrics comprised of single wall nanotubes or multi wall nanotubes (orsome combination, thereof). The methods of the present disclosure canalso be used to arrange nanotube elements within nanotube fabricscomprised of metallic nanotubes or semiconducting nanotubes (or somecombination, thereof).

In certain applications it may be desirable to arrange only a portion ofa nanotube fabric into an ordered network of nanotube elements. Suchapplications might require a fabric to have certain regions ordered andother regions unordered or might require that the overall porosity of ananotube fabric be reduced by a preselected value, such as would beachieved by only partially ordering a nanotube fabric. The methods ofthe present disclosure are well suited to such applications (as comparedwith previously known methods for adjusting the positions of nanotubeelements within a nanotube film) as the degree to which a nanotubefabric is ordered is easily controlled by modulation of the magnitude ofa directional force and the number of times that directional force istranslated across the nanotube fabric (that is, the number ofiterations). The use of such parameters within the present disclosure topartially order a nanotube fabric layer (or to arrange only nanotubeswithin preselected regions of a nanotube fabric) are shown and describedin detail in the discussion of the subsequent figures.

FIG. 2A depicts a substantially unordered nanotube fabric layer 201comprising a plurality of nanotube elements 210 deposited in a pluralityof orientations with respect to each other. Within such a nanotubefabric layer 201, gaps and voids between the nanotube elements 210 areevident throughout the fabric layer 201. Taken another way, the nanotubefabric layer 201 depicted in FIG. 2A might be considered to have a lowdensity of nanotube elements 210, with a relatively low number ofnanotube elements 210 per unit of cross-sectional area. FIG. 2B is anSEM image depicting a nanotube fabric layer 202 analogous to theunordered nanotube fabric layer 201 depicted in FIG. 2A.

FIG. 2C depicts a nanotube fabric layer 203 comprising a network ofsubstantially ordered nanotube elements 210. That is, the nanotubeelements 210 within nanotube fabric layer 203 are arranged in asubstantially uniform arrangement such that adjacent nanotube elements203 group together along their sidewalls, substantially eliminating gapsbetween nanotube elements. Taken another way, the ordered nanotubefabric layer 203 depicted in FIG. 2C might be considered to have a highdensity of nanotube elements 210, with a relatively high number ofnanotube elements 210 per unit of cross-sectional area. FIG. 2D is anSEM image depicting a nanotube fabric layer 204 analogous to the orderednanotube fabric layer 203 depicted in FIG. 2C.

It should be noted that the illustrations within FIGS. 2A and 2C havebeen provided simply to illustrate the methods of the present disclosureand have been rendered in such a way as to aid in the explanation ofthese methods. In particular, the relative sizes, positions, and densityof the nanotube elements 210 depicted within FIGS. 2A and 2C have beendesigned such as to logically illustrate the relative orientation changebetween an unordered (FIG. 2A) and an ordered (FIG. 2C) nanotube fabriclayer and have not been drawn to a uniform scale. Indeed, as will beclear to those skilled in the art, within both exemplary nanotube fabriclayers 201 and 203, nanotube elements 210 would be packed much closertogether with substantial overlapping and contact between adjacentnanotube elements 210. Further, gap sizes between individual nanotubeelements 210 would be much smaller relative to the size of nanotubeelements 210. FIGS. 2B and 2D (actual SEM images of unordered andordered nanotube fabrics, respectively) have been included to providerealistic images of such fabrics to complement the essentially schematicrepresentations depicted in FIGS. 2A and 2C.

FIGS. 3A-3F illustrate an exemplary process for rendering asubstantially unordered nanotube fabric layer (such as the nanotubefabric layers 201 and 202 depicted in FIGS. 2A and 2B) into an orderednetwork of nanotube elements (such as in the nanotube fabric layers 203and 204 depicted in FIGS. 2C and 2B). The exemplary process detailed inFIGS. 3A-3F has been intended to introduce and facilitate the discussion(on a relatively high level) of the methods of the present disclosure,specifically the use of a directional force to render an unorderednanotube fabric layer into an ordered network of nanotube elements. Assuch, while the exemplary process detailed in FIGS. 3A-3F initiallyintroduces the use of a rolling process to apply a directional force forpurposes of this overview, such a process will be discussed in greaterdetail within the discussion of FIGS. 7A-7C. Further, the presentdisclosure will also detail (in subsequent figures) a plurality of otherprocesses for applying such a directional force to a nanotube fabriclayer, including rolling, rubbing, polishing, and cryokineticimpingement.

Within the exemplary process illustrated in FIGS. 3A-3F, a substantiallyunordered nanotube fabric layer is first formed via three depositionoperations. That is, three deposition operations—for example, three spincoating operations—are performed to realize an unordered nanotube fabriclayer formed via three separately deposited layers of nanotube elements,each subsequent layer formed over the previously formed layer. Aspreviously discussed, such unordered nanotube fabric layers can berealized through a plurality of deposition methods such as, but notlimited to, spin coating, spray coating, dip coating, silk screenprinting, and gravure printing. Further, within some applications CVDgrowth of nanotubes on a material surface may be used to realize anunordered nanotube fabric layer. The thickness of the individuallydeposited layers can be selected through a plurality of factors,including, but not limited to, the concentration of the nanotubeapplication solution or the rotary speed of the substrate used in a spincoating operation. Further, while the exemplary process illustrated inFIGS. 3A-3F depicts specifically three deposition operations, theformation of a nanotube fabric layer is not limited in this way. Indeed,dependent on the needs of a specific application, such a nanotube fabriclayer might be formed within a single deposition operation or withinseveral deposition operations.

As will be detailed in the discussion of FIGS. 3A-3F below, a rollerapparatus is used to apply a directional force over the unorderednanotube fabric layer. Within this exemplary process, this directionalforce is translated across the unordered nanotube fabric layer along alinear path, adjusting the underlying nanotube elements into asubstantially uniform orientation parallel to this linear path. Withinsome applications, the individually deposited layers will also compressinto each other under the applied directional force, reducing thethickness of the overall layer as a result. In this way, a region of anunordered nanotube fabric layer is rendered into an ordered network ofnanotube elements.

Within the exemplary process depicted in FIGS. 3A-3F, a force normal tothe plane of the nanotube fabric layer is used to apply the rollerapparatus against the nanotube fabric layer, resulting in a downwardpressure over the nanotube fabric layer as the roller apparatus istranslated across. In some embodiments this pressure is relatively small(for example, substantially only the result of weight of the rollerelement itself—e.g., on the order of ten Pascals—as it is translatedacross the nanotube fabric layer). In other embodiments this force islarger (for example, on the order of two hundred Pascals). Thisincreased pressure (provided by the applied normal force) between theroller apparatus and the nanotube fabric layer and increases thedirectional force translated across the nanotube fabric layer. Asmentioned above, such a rolling operation (as well as the use of anormal force to apply increased pressure between a roller apparatus anda nanotube fabric layer) will be discussed in greater detail in thediscussion of FIGS. 7A-7C.

Referring now to FIG. 3A, in a first process step 301 a substrateelement 310 is provided. This substrate element 310 can be formed from aplurality of materials as best fits the needs of a specific application.For example, in some applications substrate element 310 may be a siliconwafer. In other applications, substrate element 310 may be a layer ofconductive material, such as, but not limited to, tungsten, aluminum,copper, nickel, palladium, titanium nitride, and tungsten nitride. Instill other applications, substrate element 310 may be a layer ofsemiconducting material such as, but not limited to, silicon and galliumarsenide. In other applications, substrate element 310 may be a layer ofdielectric material such as, but not limited to, silicon oxide andaluminum oxide. In other applications, substrate element 310 may be alayer of organic semiconducting material such as, but not limited to,polyfluorene polythiophenes, polyacetylenes, polypyrroles, polyanilines,poly(p-phenylene sulfide), and poly(p-phenylene vinylene)s. In someapplications substrate element 310 may be formed of a rigid material,such as, but not limited to, metal (e.g., steel or aluminum), ceramic,or glass. In other applications it may be formed of a flexible materialsuch as a plastic film or sheet—e.g., polyethylene terephthalate (PET),polymethylmethacrylate, polyamides, polysulfones, and polycyclicolefins.

Referring now to FIG. 3B, in a next process step 302 a first layer ofunordered nanotube elements 320 is formed over the substrate element310. This first layer may be formed, for example, via a spin coatingoperation, a spray coating operation, a dip coating operation, a silkscreen printing operation, and gravure printing operation as previouslydiscussed. In some embodiments, such a layer may also be formed throughCVD growth of nanotubes on a material surface. Referring now to FIG. 3C,in a next process step 303 a second layer of unordered nanotube elements320 is formed over the first layer. Referring now to FIG. 3D, in a nextprocess step 304 a third layer of unordered nanotube elements 320 isformed over the second layer. In this way, a nanotube fabric layercomprising essentially three individually deposited layers ofsubstantially unordered nanotube networks is formed over substrateelement 310.

Referring now to FIG. 3E, in a next process step 305 a rolling apparatus330 is used to apply a directional force over the deposited nanotubefabric layer. This applied directional force is translated over thesurface of the unordered nanotube fabric layer along linear direction390. The rolling apparatus 330 includes rolling element 330 a and ispassed over the deposited nanotube fabric layer in order to adjust theunderlying nanotube elements into a substantially uniform orientationparallel to the rolling direction 390. In some applications the rollingapparatus 330 is passed over the deposited nanotube fabric layer once.In other applications the rolling apparatus 330 is passed over thedeposited nanotube fabric layer multiple times (for example, on theorder of 50 times or, in another example, on the order of 250 times)following substantially the same linear path with each pass. Though notillustrated in FIG. 3E, in some embodiments an intermediate barrierlayer of pliable material (such as, but not limited to, a layer of PET)is situated over the deposited nanotube fabric layer prior to theapplication of rolling apparatus 330. Rolling element 330 a can beformed from a plurality of materials, including, but not limited to,metal (such as, but not limited to, iron, cobalt, nickel, zinc,tungsten, chromium, manganese, magnesium, titanium, aluminum, and theiralloys including family of steels), polymers including rubbers, plastics(including polystyrene), melamine, silicone, polycarbonate,polyethylene, porcelain, glasses (including silicon oxide and othercrystalline solids), alumina, silicon carbide, and wood.

Referring now to FIG. 3F, the rolled region 350 of deposited nanotubefabric layer has been rendered into an ordered network of nanotubeelements 320 (as depicted in structure 306). As depicted in FIG. 3F,this rolled region 350 exhibits essentially no gaps or voids betweennanotube elements 320. In some embodiments, an additional process stepmight be used to provide a high temperature anneal process to theordered network of nanotube elements 320—for example, baking thesubstrate element 310 and nanotube fabric layer within the range of 400°C. to 625° C. (as dependant on the needs of the specific application)for given time (for example, on the order of thirty minutes). This hightemperature anneal process, in some embodiments, is helpful inpreventing subsequent exposure to chemical and physical conditionsduring further processing of the fabric from disturbing the orderednanotube fabric layer once it has been oriented. For example, in certainembodiments such a high temperature anneal process can render theordered nanotube fabric into a substantially hydrophobic state,preventing the arranged nanotubes from reacting when exposed to water.However, it should be noted that in some embodiments a sensitivity tocertain chemical or physical conditions can be beneficial to a specificapplication. For example, an ordered nanotube fabric that exhibits alocalized change within the fabric when exposed to a specific chemicalor physical condition would be useful in a sensor application or withinan application for storing and/or recording information.

It should be noted that the illustrations within FIGS. 3A-3F have beenprovided simply to illustrate the methods of the present disclosure andhave been rendered in such a way as to aid in the explanation of thesemethods. In particular, the relative sizes of the different structuralelements within FIGS. 3A-3F have not been drawn to a uniform scale.Indeed, as will be clear to those skilled in the art, nanotube elements320 would be much smaller than rolling apparatus 330, as would actualgap sizes between such elements 320.

While the exemplary process depicted in FIGS. 3A-3F applies adirectional force along a single linear path in order to render ananotube fabric layer into an ordered state, the methods of the presentdisclosure are not limited in this regard. Indeed, in some applicationsmultiple directional forces may be applied sequentially in differentdirections to realize a plurality of regions within the nanotube fabriclayer wherein the nanotube elements within adjacent ordered regions areoriented in different directions. In other applications, a rotationaldirectional force may be applied over an unordered nanotube fabric layerto form regions of ordered nanotube elements within the nanotube fabriclayer. FIGS. 4-6 illustrate the application of different directionalforces in order to render nanotube fabrics into networks of orderednanotube elements according to the methods of the present disclosure.

Referring now to FIG. 4, an exemplary process for rendering an unorderednanotube fabric layer into a network of ordered nanotube elementssubstantially oriented along a single direction through the use of anapplied linear force is depicted. At the start of the exemplary process,an unordered nanotube fabric layer 401 comprising a plurality ofnanotube elements 410 is provided. A linear directional force is thenapplied over the unordered nanotube fabric layer 401 (for example, arolling force applied fifty times in the direction indicated in FIG. 4)to realize partially ordered nanotube fabric layer 402. Partiallyordered nanotube fabric layer 402 exhibits regions of ordered nanotubeelements 420 wherein nanotube elements have been oriented in thedirection of the applied force. The nanotube elements in these regions420 are grouped together along their sidewalls, resulting in essentiallyno gaps or voids within those regions 420. A linear directional force isthen applied again along the same direction (for example, the samerolling force applied an additional fifty times) to realize orderednanotube fabric layer 403. Within ordered nanotube fabric layer 403,essentially all of the nanotube elements 410 have been rendered into asubstantially uniform orientation along the direction of the appliedforce. As depicted in FIG. 4, ordered nanotube fabric layer 403 issubstantially free of gaps and voids.

Referring now to FIG. 5, an exemplary process for rendering an unorderednanotube fabric layer into a network of ordered nanotube elementssubstantially oriented in multiple directions through the use of linearforce applied along multiple directions is depicted. At the start of theexemplary process, an unordered nanotube fabric layer 501 comprising aplurality of nanotube elements 510 is provided. A first lineardirectional force is then applied over the unordered nanotube fabriclayer 501 in a first direction (as indicated n FIG. 5) to realize firstpartially ordered nanotube fabric layer 502. This first linear force maybe, for example, a rubbing force applied twenty times. First partiallyordered nanotube fabric layer 502 exhibits regions of ordered nanotubeelements 520 wherein nanotube elements have been oriented in thedirection of the first applied force. The nanotube elements in theseregions 520 are grouped together along their sidewalls, resulting inessentially no gaps or voids within those regions 520. A second lineardirectional force is then applied along a second direction (as indicatedin FIG. 5) to realize second partially ordered nanotube fabric layer503. This second linear force may be, for example, another rubbing forceapplied twenty times in the second direction. Second partially orderednanotube fabric layer 503 exhibits a plurality of regions 530 whereinthe nanotube elements have been oriented in the direction of the secondapplied force.

It should be noted that the nanotube elements 510 within the orderedregions 520 (that is, those nanotube elements oriented by theapplication of the first linear force) are, in general, substantiallyunaffected by the application of the second linear directional force.That is, once a region of nanotube elements 510 has been sufficientlyrendered into an ordered network substantially oriented along a firstdirection, the nanotube elements within that region will tend to remainin their ordered state, resisting a change in orientation significantlymore so than unordered nanotube elements, even when subjected to a forceapplied in a second direction. It should be noted, however, that in someembodiments, a persistent application of the second linear directionalforce will reorder an ordered network of nanotubes along the directionof the second directional force.

As depicted in FIG. 5, second partially ordered nanotube fabric layer503 includes regions 520 ordered along a first direction and regions 530oriented along a second direction. Within both sets of regions (520 and530), the nanotube elements 510 are grouped together along theirsidewalls, resulting in those regions (520 and 530) being essentiallyfree of gaps and voids. The remaining regions of unordered nanotubeelements 510 within second partially ordered nanotube fabric layer 503could be rendered into an ordered state through the application of anadditional directional force.

Referring now to FIG. 6, an exemplary process for rendering an unorderednanotube fabric layer into a network of ordered nanotube elements (withdifferent regions of the fabric layer substantially oriented in multipledirections) through the use of rotational directional force is depicted.At the start of the exemplary process, an unordered nanotube fabriclayer 601 comprising a plurality of nanotube elements 610 is provided. Arotational directional force is then applied over the unordered nanotubefabric layer 601 to provide partially ordered nanotube fabric layer 602.Such a rotational directional force may be applied, for example, byrotating a wool polishing pad at approximately sixty rotations perminute for approximately ninety seconds (an apparatus suitable forapplying such a rotational directional force is illustrated in FIGS. 11Aand 11B and discussed in detail below). Partially ordered nanotubefabric layer 602 exhibits several regions of ordered nanotube elements620 wherein nanotube elements have been grouped together along theirsidewalls, resulting in essentially no gaps or voids within thoseregions 620. Due to the rotational directional force, these orderedregions 620 are oriented in different directions. The remaining regionsof unordered nanotube elements 610 within partially ordered nanotubefabric layer 602 could be rendered into an ordered state through theapplication of an additional directional force.

It should be noted that the partially ordered nanotube fabric layerswithin the previous illustrations (that is, nanotube fabric layers 402,502, and 602 in FIGS. 4, 5, and 6, respectively) depict nanotube fabriclayers initially beginning to order themselves into relatively narrowbands responsive to an applied directional force. In this respect, itshould be further noted, these illustrations are consistent with thepartially ordered nanotube fabrics depicted within the exemplary SEMimages of FIGS. 20A and 25B. Without wishing to be bound by theory, itis believed that within certain embodiments a certain number of nanotubeelements within the unordered nanotube fabric will originally beoriented in the direction of the applied directional force. Responsiveto the applied directional force, nanotube elements adjacent to thesecertain nanotube elements—but positioned in slightly differentorientations—will tend to adjust their orientation to match that of thenanotube elements already oriented in the desired direction. Withinthese embodiments, it is believe that increased application (repetition)of a directional force will tend to adjust more and more of theunordered nanotube elements into an orientation consistent with theseoriginal nanotube elements until, ultimately, the entire nanotube fabriclayer is adjusted into a substantially uniform orientation.

Having introduced the methods of the present disclosure on a relativelyhigh level—specifically the use of a directional force in one or moredirections to arrange a substantially unordered (or, in someapplications, a partially ordered) nanotube fabric layer into an orderednetwork of nanotube elements—the present disclosure will now discuss aplurality of methods for applying such a directional force in detail.Specifically, FIGS. 7A-7B detail the use of a rolling apparatus to applya directional force. FIGS. 8A-8B detail the use of a rubbing apparatusto apply a directional force in a linear motion. FIGS. 9A-9B detail theuse of a rubbing apparatus to apply a directional force in an arcingmotion. FIGS. 10A-10B detail the use of a polishing apparatus to apply adirectional force in a linear direction. FIGS. 11A-11B detail the use ofa polishing apparatus to apply a rotational directional force. FIGS.12A-12B detail the use of a cryokinetic impingement apparatus to apply adirectional force. And, FIGS. 13A-13B detail the use of a roll-to-rollpolishing apparatus to apply a rotational directional force on a largescale.

Referring now to FIGS. 7A-7B, a rolling apparatus suitable for applyinga linear directional force across a nanotube fabric layer is depicted.As described briefly in the exemplary process depicted in FIGS. 3A-3F,in some applications a directional rolling force can be applied byrolling a cylindrical element over a formed nanotube layer one or moretimes. This cylindrical element can be formed from a plurality ofmaterials, including, but not limited to, metal (such as, but notlimited to, iron, cobalt, nickel, zinc, tungsten, chromium, manganese,magnesium, titanium, aluminum, and their alloys including family ofsteels), polymers including rubbers, plastics (including polystyrene),melamine, silicone, polycarbonate, polyethylene, porcelain, glasses(including silicon oxide and other crystalline solids), alumina, siliconcarbide, and wood. In some embodiments, this cylindrical element isapplied directly to the nanotube fabric layer. In other embodiments, anintermediate layer—such as, but not limited to, a layer of polyethyleneterephthalate (PET) film—is situated between the nanotube fabric layerand the surface of the cylindrical element. In some embodiments thecylindrical element is rolled over the formed nanotube layer once. Inother embodiments the cylindrical element is rolled over the formednanotube layer on the order of fifty times. In still other embodimentsthe cylindrical element is rolled over the formed nanotube layer on theorder of two hundred and fifty times. In some embodiments, no additionaldownward force is applied to the cylindrical element as it is passedover the nanotube fabric layer—that is, substantially only the weight ofthe cylindrical element is responsible for the downward force applied(providing, for example, on the order of 500 Pascals of pressure overthe nanotube fabric layer as the roller apparatus is translated across).In other embodiments an additional downward force (for example, on theorder of fifty Newtons, or in another example on the order of fivehundred Newtons) is applied to the cylindrical element—for example,through the use of a pressing mechanism or through the use of a rollingapparatus which passes a nanotube fabric coated substrate elementthrough a pair of cylindrical rollers held apart a fixed distance. Insuch embodiments, this additional downward force provides significantlymore pressure (for example, on the order of 20,000 Pascals) over thenanotube fabric layer as the roller apparatus is translated across.

FIGS. 7A and 7B are a perspective drawing and an application diagram,respectively, depicting an exemplary rolling apparatus 700 suitable forapplying a rolling force over a deposited nanotube fabric layeraccording to the methods of the present disclosure. A substrate element710 coated with a nanotube fabric layer is passed between upper rollerelement 720 and lower roller element 730 along direction 790. Upperroller element 720 is adjustable within frame 750 through adjustmentmechanism 740 such that a desired rolling force may be applied to thesubstrate element 710 along direction 795 and translated across ananotube fabric layer deposited on the substrate element 710 alongdirection 790 as it is passed between upper and lower roller elements(720 and 730, respectively). In this way, a rolling force can be appliedacross a nanotube fabric layer one or more times, rendering the nanotubelayer into a network of ordered nanotube elements. FIGS. 19A-19C(discussed in detail below) are SEM images depicting an exemplarynanotube fabric layer after the application of such a directionalrolling force.

Referring now to FIGS. 8A-8B, a rubbing apparatus suitable for applyinga linear directional force across a nanotube fabric layer is depicted.In some applications, a directional rubbing force can be applied to ananotube fabric layer by first forming a nanotube fabric layer over asubstrate layer and subsequently sliding that nanotube fabric layeracross a rubbing surface (the nanotube fabric layer in direct contactwith the rubbing surface) one or more times (as is depicted in theexemplary apparatus of FIGS. 8A-8B). In other applications, a rubbingsurface can be moved over a formed nanotube fabric layer (that is, thenanotube fabric layer is fixed in place while a rubbing element is movedacross—such as the exemplary apparatus illustrated in FIG. 21). Withinthe methods of the present disclosure, a rubbing element comprises asheet of flat material which can provide a smooth interface to ananotube fabric to minimize abrasion or scratching of the nanotubefabric. Such a rubbing surface or rubbing element can be formed from aplurality of materials, including, but not limited to, the smoothsurface of an elemental silicon wafer, polytetrafluoroethylene (PTFE),cellulose acetate, cellulose (e.g., rayon), polyesters (e.g.,polyethylene terephthalate and polybutyrate), polyamides (e.g.,commercially available nylons), polymeric materials (in fibrous, foam,fabric, or film forms) including blends of the aforementioned polymermaterial types or natural materials (e.g., leather, cellulosic materialas fiber or sheets), and semi-rigid slurries (such as, but not limitedto, semi-rigid slurries of starch and water).

In some embodiments the nanotube fabric layer is passed over the rubbingsurface once. In other embodiments the nanotube fabric layer is passedover the rubbing surface on the order of twenty times. In still otherembodiments the nanotube fabric layer is passed over the rubbing surfaceon the order of two hundred times. In some embodiments the nanotubefabric layer is passed over the rubbing surface with a unidirectionalmovement (that is, only propelled forward against the rubbing surface aset distance from an initial position, then lifted from the rubbingsurface and returned to this initial position for subsequent rubbingpasses). In other embodiments the nanotube fabric layer is passed overthe rubbing surface with a bidirectional movement (that is, propelledforward against the rubbing surface a set distance from an initialposition and then pulled back against the rubbing surface to the initialposition again).

In some embodiments a normal force (applied orthogonally with respect tothe directional force) is applied either to the substrate element or tothe rubbing surface (or both) such as to modulate the pressure betweenthe two materials, and thus modulate the magnitude of the directionalforce as it is translated across the nanotube fabric layer. In someembodiments the pressure provided by this additional downward force ison the order of 300 to 800 Pascals. In other embodiments the pressureprovided by this additional downward force may be greater than 1000Pascals. In certain embodiments, such pressures may increase the speedor quality of ordering within the underlying nanotube fabric layer solong as such pressures do not damage or otherwise ablate the fabriclayer.

FIGS. 8A and 8B are a perspective drawing and an application diagram,respectively, depicting an exemplary rubbing apparatus 800 well suitedfor applying a directional rubbing force over a nanotube fabric layeraccording to the methods of the present disclosure. Within this example,a nanotube fabric is formed on a substrate element 810, and thesubstrate element 810 is then moved across a fixed rubbing surface 820.The substrate element 810 (coated with a nanotube fabric layer) issecured against a vacuum plate 840 (using vacuum pump 870) and placedagainst rubbing surface 820 such that the nanotube fabric layer isagainst rubbing surface 820. A carrier mechanism 850 is secured aroundvacuum plate 850 and used to propel substrate element 810 across rubbingsurface 820 along direction 890. A weighted element 860 is positionedatop vacuum plate 840 such as to increase the pressure applied betweenthe nanotube fabric layer and the rubbing surface 820. The additionalforce provided by weighted element 860 in direction 895 is translatedacross the nanotube fabric layer in direction 890 as substrate element810 is propelled across rubbing surface 820. In this way, a rubbingforce can be applied across a nanotube fabric layer one or more times,rendering the nanotube layer into a network of ordered nanotubeelements. FIGS. 20A-20C, 21A-21C, and 22A-22C (discussed in detailbelow) are SEM images depicting nanotube fabric layers after theapplication of such a directional rubbing force.

Referring now to FIGS. 9A-9B, a rubbing apparatus suitable for applyinga directional force in an arcing motion across a nanotube fabric layeris depicted. In some applications a directional rubbing force can beapplied to a nanotube fabric layer by passing a rubbing element over thesurface of a formed nanotube fabric layer in an arcing motion. Forexample a chemical mechanical polishing (CMP) machine can be used topass a rubbing pad back and forth in a shallow arc over a nanotubefabric layer deposited over a substrate element (the substrate held in afixed position on a vacuum plate within the CMP machine). Such a rubbingpad might typically be formed of a polyurethane material, but may becomprised of other materials, including, but not limited to, polyesterand polyamide microfibers, other forms of polyester (e.g., fibrous,foam, fabric, and film forms of polyester), polyamide and otherpolymers, styrene, polyvinylalcohol foam, cotton, wool, cellulose, andrayon.

FIGS. 9A and 9B are a perspective drawing and an application diagram,respectively, depicting a first exemplary rubbing apparatus 900 suitablefor applying a directional force over a deposited nanotube fabric layerin an arcing motion according to the methods of the present disclosure.A substrate element 910 coated with a nanotube fabric layer is placedwithin a carrier assembly 940. The carrier assembly 940 is moved byadjustable arm 950 rotating on pivot mechanism 960 in an arc acrossrubbing surface 920 (fixed in place within device surface 970) such thatthe nanotube fabric layer deposited on the surface of substrate element910 is passed over rubbing surface 920 in direction 990. In this way, arubbing directional force can be applied across a nanotube fabric layerone or more times, rendering the nanotube layer into a network ofordered nanotube elements. FIGS. 23A-23C (discussed in detail below) areSEM images depicting nanotube fabric layers after the application ofsuch a directional rubbing force. It should be noted, that as show inFIGS. 23A-23C, a nanotube fabric ordered via a rubbing directional forceapplied in a wide arcing motion will tend to order in a substantiallylinear direction.

Referring now to FIGS. 10A-10B, a polishing apparatus suitable forapplying a directional force in a linear motion across a nanotube fabriclayer is depicted. A cylindrical polishing element—e.g., as a rigidcylinder coated with a soft polishing material (such as, but not limitedto, wool and velour) and rotated about its long axis—can be rotated onthe order of fifteen to twenty rotations per minute (RPM) as it istranslated linearly over a region of the nanotube fabric layer (with therotating cylinder in contact with the nanotube fabric layer) repeatedlyfor several minutes. Suitable polishing material may include, but is notlimited to, polyester and polyamide microfibers, other forms ofpolyester (e.g., fibrous, foam, fabric, and film forms of polyester),polyamide and other polymers, styrene, polyvinylalcohol foam, cotton,wool, cellulose, and rayon. The force applied to the polishing materialas it is translated across the nanotube fabric layer may be selected asto increase the pressure between the two materials. For example, in someembodiments the applied force is selected such as to compress the nap ofthe polishing material against the nanotube fabric layer byapproximately fifty percent. In some embodiments it may be important toprevent this force from compressing the nap of the polishing materialcompletely and allowing the backing of the polishing material to comeinto physical contact with the nanotube fabric layer. Within suchembodiments, such contact may result in the backing layer scratching orotherwise damaging the nanotube fabric layer. As the polishing materialis passed across the nanotube fabric layer, this additional force istranslated across the nanotube fabric layer imparting a directionalforce over the fabric. In some embodiments this applied force may resultin a pressure on the order of 5 to 100 Pascals across the nanotubefabric layer. In other embodiments this applied force may result in apressure on the order of 500 Pascals.

FIGS. 10A and 10B are a perspective drawing and an application diagram,respectively, depicting a second exemplary polishing apparatus 1000suitable for applying a directional force over a deposited nanotubefabric layer according to the methods of the present disclosure. Asubstrate element 1010 coated with a nanotube fabric layer is secured inplace on a vacuum table 1070. A cylindrical polishing element 1020 ispositioned within track element 1050 such that the polishing materialcovering the surface of cylindrical polishing element 1020 is placedagainst the nanotube fabric layer deposited over substrate element 1010.Cylindrial roller 1020 is rotated in direction 1090 (for example, at 60rpm) and then moved within track element 1050 such that the forceapplied by the cylindrical polishing element 1020 is translated acrossthe nanotube fabric layer deposited on substrate element 1010. In thisway, a polishing force can be applied across a nanotube fabric layer oneor more times, rendering the nanotube layer into a network of orderednanotube elements. FIGS. 24A-24C (discussed in detail below) are SEMimages depicting nanotube fabric layers after the application of such apolishing directional force.

Referring now to FIGS. 11A-11B, a polishing apparatus suitable forapplying a rotational directional force over a nanotube fabric layer isdepicted. A rotational directional force can be applied to a nanotubefabric layer by rotating a polishing element over the surface of aformed nanotube fabric layer. For example a polishing pad can be placedover a nanotube fabric layer and rotated for a set time (for example, onthe order of ninety seconds). Suitable material for the polishingelement may include, but is not limited to, polyester and polyamidemicrofibers, other forms of polyester (e.g., fibrous, foam, fabric, andfilm forms of polyester), polyamide and other polymers, styrene, polyvinylalcohol foam, cotton, wool, cellulose, and rayon. In someembodiments, a polishing material may be selected according to aspecific denier specification (denier being an attribute of textilesindicating the weight in grams of 9000 meters of a fiber). In someembodiments an additional force is applied to the polishing element asit is rotated over the nanotube fabric layer as to increase the pressurebetween the two materials. As the polishing element is rotated, thisadditional force is translated across the nanotube fabric layer. In someembodiments this applied force may result in a pressure on the order oftwo to five Pascals across the nanotube fabric layer. In otherembodiments this applied force may result in a pressure on the order of100 Pascals.

FIGS. 11A and 11B are a perspective drawing and an application diagram,respectively, depicting a exemplary apparatus 1100 suitable for applyinga rotational polishing force over a deposited nanotube fabric layeraccording to the methods of the present disclosure. A substrate element1110 coated with a nanotube fabric layer is secured in place on a vacuumtable 1170. A polishing element 1120 is fixed within rotating assembly1140 and positioned with adjustment arm 1150 such that the polishingelement 1120 is placed against the nanotube fabric layer deposited oversubstrate element 1110. Polishing element 1120 is then rotated in placein direction 1190 (for example, at sixty rotation per minute for sixtyseconds). In this way, a rotational polishing force can be appliedacross a nanotube fabric layer, rendering the nanotube layer into anetwork of ordered nanotube elements. FIGS. 25A-25C (discussed in detailbelow) are SEM images depicting nanotube fabric layers after theapplication of such a rotational polishing force.

Referring now to FIGS. 12A-12B, a cryokinetic impingement apparatussuitable for applying a directional force over a nanotube fabric layeris depicted. A directional polishing force can be applied to a nanotubefabric layer through the use of a cryokinetic process. FIGS. 12A-12Billustrate an exemplary cryokinetic impingement device well suited foruse with the methods of the present disclosure. Within such a device, anapplication wand 1250 is used to direct a spray of frozen particles 1220at a shallow angle (for example, on the order of 15 degrees with respectto the plane of the nanotube fabric layer) over a nanotube fabric layer1210 at a relatively high velocity (for example, propelled with apressure on the order of 60 PSIG). The impact of these frozen particles1220 provides a directional force which is translated across thenanotube fabric layer 1210 as application wand 1250 is moved alongdirection 1290. Within such a system, frozen particles 1220 may berice-sized particles (for example, on the order of 0.125 inchesdiameter) of a frozen gas such as, but not limited to, carbon dioxide(CO₂) or argon.

FIGS. 12A and 12B, a perspective drawing and an application diagram,respectively, of a cryokinetic impingement system are depicted. Ananotube fabric coated wafer 1210 is secured to vacuum plate 1230 suchas to hold it in place during the polishing operation. An applicationwand 1250 is fed by an air hose 1270 and a pellet supply hose 1260 suchas to direct a spray of frozen pellets 1220 across nanotube fabriccoated wafer 1210. Controls 1280 on the pelletizer unit allow forcontrol of the velocity and quantity of stream 1220. Within an exemplarypolishing operation, application wand 1250 is positioned at a shallowangle and moved across nanotube fabric covered wafer 1210 alongdirection 1290.

Though not illustrated in FIGS. 12A and 12B, in some embodiments anintermediate barrier layer of pliable material—such as, but not limitedto, a layer of PET, a plastic membrane (e.g., Saran wrap, based uponpolyvinylidene chloride), or a thin foil film—is situated over thedeposited nanotube fabric layer prior to the application of thecryokinetic spray 1220. Within such embodiments, this layer of pliablematerial may be used to protect the underlying nanotube fabric layer1210 and guard against ablation of the individual nanotube elementsunder the high velocity spray 1220. In some embodiments this layer ofpliable material may also be useful in efficiently transferring theforce cryokinetic spray to the nanotube fabric. In this way, a polishingforce can be applied across a nanotube fabric layer one or more times,rendering the nanotube layer into a network of ordered nanotubeelements. FIGS. 28A-28D (discussed in detail below) are SEM imagesdepicting nanotube fabric layers after the application of such acryokinetic impingement force.

In other applications a similar (with respect to the above describedcryokinetic impingement operation) ordering operation may be realizedthrough the use of a jet of high pressure gas or liquid (e.g., an airgun). Within such a high pressure flow polishing operation, an air gunmay be used to flow a gas (such as, but not limited to, nitrogen) overan unordered nanotube fabric layer to render that fabric layer into anordered network of nanotube elements. As with the cryokineticimpingement operation, in some embodiments a high pressure flowoperation might employ a pliable protective layer—such as, but notlimited to, a layer of PET, a plastic membrane (e.g., Saran wrap, basedupon polyvinylidene chloride), or a thin foil film—over the nanotubefabric layer during the air flow operation. An exemplary high pressureair flow polishing operation is depicted in FIGS. 32A-32D and describedin detail below.

Referring now to FIGS. 13A-13B, a roll-to-roll polishing apparatussuitable for applying a directional force over a nanotube fabric layeris depicted. A flexible material 1310 (such as, but not limited to,paper, plastic, or metallic foil) coated with a substantially unorderednanotube fabric 1310 a is transferred between a first roller 1350 and asecond roller 1360 along direction 1395. Within the exemplaryroll-to-roll polishing apparatus depicted in FIGS. 13A and 13B, acylindrical polishing element 1320 is rotated along direction 1320against the unordered nanotube fabric layer as it is linearly translatedbeneath it between the first and second rollers (1350 and 1360,respectively). The composition and use of such a cylindrical polishingelement 1320 is depicted and described in detail within the discussionof FIGS. 10A and 10B above. The directional force applied by cylindricalpolishing element 1320 arranges the nanotube elements within unorderednanotube fabric layer 1310 a (deposited by applicator 1340) into anetwork of ordered nanotubes 1310 b. In this way, a large scale nanotubefabric can be arranged into an ordered nanotube fabric layer.

It should be noted that while a cylindrical polishing element 1320 isdepicted in FIGS. 13A and 13B, the methods of this aspect of the presentdisclosure are not limited in this regard. Indeed, any of the rolling,rubbing, and polishing methods described within the present disclosuremay be used with a roll-to-roll system as depicted in FIGS. 13A and 13B.Further, in certain applications a roll-to-roll polishing apparatus suchas is depicted in FIGS. 13A and 13B might further include an applicatormechanism and drying mechanism which can be used to deposit and dry ananotube fabric over flexible material 1310 as it is transitionedbetween first roller 1350 and second roller 1360

In other applications a layer of piezoelectric material may be placedover an unordered nanotube fabric layer and used to apply a directionalforce to the fabric layer. Within such applications, the piezoelectricmaterial will vibrate in response to certain electrical stimuli,effectively generating a rubbing force which is translated over thenanotube fabric layer. In some embodiments, a layer of piezoelectricmaterial may be shaped such as to apply such a directional force only toone or more preselected regions within the nanotube fabric layer. Withinsuch embodiments, those preselected regions may be rendered into orderednetworks of nanotube elements, leaving the remaining regionssubstantially unordered. Such a selectively ordered nanotube fabriclayer would be useful, for example, as a masking or imprinting devicewithin a photolithography operation. An exemplary piezoelectric rubbingoperation is depicted in FIGS. 30A-30D and described in detail below.

As previously discussed, a CMP machine—a polishing/planarizing apparatustypically readily available in semiconductor fabrication facilities—is adevice well suited (within certain applications) for applying adirectional force over a nanotube fabric. For example, a CMP machine canbe used to pass a polishing element or a rubbing element over a nanotubefabric layer deposited over a silicon wafer in an arcing or a linearpath (in an operation similar to that of the exemplary apparatusdepicted in FIGS. 9A and 9B). In another example, a CMP machine can beused to rotate a polishing element or a rubbing element over a nanotubefabric deposited over a silicon wafer (in an operation similar to thatof that of the exemplary apparatus depicted in FIGS. 11A and 11B).

Within certain applications a polishing element or a rubbing element canbe applied to the nanotube fabric layer using a lubricating medium. Suchlubricating media can include, but are not limited to, water, halocarbon(included, but not limited to, liquids including halogen containingalcohols, alkyl nitrites, alkanols, organic amines, fluorinatedcompounds and perfluorocarbons, perfluorohexane, perfluoroheptanechlorocarbons, perfluorinated or substantially fluorinated organiccompounds including perfluorohexane, perfluoro(2-butyl-tetrahydrofurane,and perfluorinated polyether), liquefied gases (including, but notlimited to, liquid carbon dioxide (CO₂) and liquid xenon), hydrocarbonliquids (including, but not limited to, C₃-C₁₂ alkanes, C₈-C₁₆arylalkanes, C₁₀-C₂₅ arylcyloalkanes, C₆-C₁₂ aromatics, toluene, andXylene), functionalized organic liquids (including, but not limited to,those containing ketone, aldehyde, ester, ether, amide, alcohol, C₂-C₁₂ethers, DME, glymes, methanol, ethanol, propanol, butanol, acetone, andtetrahydrofuran), organo-siloxane based cyclics and linear liquids(including, but not limited to, groups of polydimethylsiloxanes cylicand linear liquids and polyphenylsiloxane cyclic and linear liquids),and solids (including, but not limited to, molybdenum disulfide, boronnitride, graphite, and styrene beads).

Within such applications a lubricating medium may facilitate theapplication of a directional force by limiting drag between a polishing(or rubbing) element and the surface of the nanotube fabric. Forexample, within an ordering operation wherein a rubbing element isapplied with relatively high pressure, a lubricating medium can be usedto ensure that the resulting directional force is applied evenly overthe entire surface of the nanotube fabric.

In some applications a lubricating medium can be applied to apolishing/rubbing pad prior to an ordering operations (for example, apolishing/rubbing pad being dampened with water). In other applicationsa lubricating medium can be deposited over a nanotube fabric prior tothe application of a polishing/rubbing pad. Within such applications,the lubrication medium is selected and/or applied in such a way as tonot result in any substantial re-suspension of nanotube elements withinthe nanotube fabric into the applied lubrication medium.

It should be noted that while the use of a lubricating medium isbeneficial in certain applications (as described above) in otherapplications it may be problematic within an ordering operation. Incertain applications, for example, the application of a lubricatingmedium can fully dislodge nanotube elements from a substrate surface. Inanother example, a lubricating medium (within certain applications) mayreact (physically or chemically) with the nanotube elements damaging orotherwise adversely affecting the unordered nanotube fabric layer.

It should also be noted that the arrangement of nanotube elements withinnanotube fabric layers via the methods of the present disclosure alsoprovides nanotube fabrics which are highly smooth as compared tounordered nanotube fabric layers. Within some applications, thesesmoother fabric layers provide optimized surfaces for the deposition ofsubsequent material layers. For example, such ordered nanotube fabriclayers may be expected to have a substantially uniform thickness acrossthe entire layer, reducing the likelihood of thin areas in the fabricwhich may, in some application, allow a subsequently deposited layer topenetrate through the nanotube fabric layer.

To this end, FIGS. 14A and 14B depict a cross section view of asubstantially unordered nanotube fabric layer 1420 deposited over asubstrate layer 1410. A top layer of material 1430 has been furtherdeposited over the unordered nanotube fabric layer 1420 to create athree-layer structure. FIG. 14A is an SEM image 1401 of this three-layerstructure, while FIG. 14B is a line drawing of the same structure. Ascan be observed in the two images (1401 and 1402), substantiallyunordered nanotube fabric layer 1420 exhibits a non-uniform thickness,providing a number of “thin spots” between substrate layer 1410 and topmaterial layer 1430.

Conversely, FIGS. 15A and 15B depict a cross section view of an orderednanotube fabric layer 1520 deposited over a substrate layer 1510. Aswith the previous structure of FIGS. 14A and 14B, a top layer ofmaterial 1530 has been further deposited over the ordered nanotubefabric layer 1520 to create a three-layer structure. FIG. 15A is an SEMimage 1501 of this three-layer structure, while FIG. 15B is a linedrawing of the same structure. As can be observed in the two images(1501 and 1502), unordered nanotube fabric layer 1520 exhibits asignificantly improved uniformity in thickness (as compared withunordered nanotube fabric layer 1420 in FIGS. 14A and 14B), providing amore uniform separation distance between substrate layer 1510 and topmaterial layer 1530.

It should also be noted that within certain embodiments an orderednanotube fabric layer would possess a decreased coefficient of friction(as compared with an unordered nanotube fabric layer) and would beuseful in the fabrication of low friction coatings. For example, a layerof nanotube fabric may be formed over the inner surface of a cylinderwithin an internal combustion engine and then rendered into an orderedstate. Such an ordered fabric could then be used to reduce thecoefficient of friction of a piston moving within the cylinder. Inanother example, ordered nanotube fabric layers may be formed over themating surfaces of gears, bearings, shafts, and other mechanicalcomponents within a mechanized system. Such coating would reduce thefriction between the mating surfaces of these components, reducing wearand extending the life of the individual components and, by extension,the system itself. In another example, such ordered nanotube fabriclayers may be used to provide nanoscale low friction surfaces andcoatings within microelectromechanical systems (MEMS).

FIGS. 16 and 17 illustrate an experiment performed on a partiallyordered nanotube fabric layer to demonstrate the reduced coefficient offriction of an ordered nanotube fabric layer as compared with anunordered nanotube fabric layer. A nanotube fabric layer 1610 was formedover a silicon substrate 1670 and cut into a strip approximately 4 cmwide and 20 cm long. The nanotube fabric layer 1610 was then selectivelyrendered into an ordered state such as to realize five regions (1710a-1710 e) along the length of the strip, as depicted in FIG. 17. Apolishing pad 1650 was then wrapped over and secured to a cleaved SiO₂wafer 1640 (approximately 4 cm by 4 cm in dimension) such as to form arigid rubbing element and placed over the selectively ordered nanotubefabric layer 1610. A weighted element 1660 (approximately 75 g) wasplaced over this rigid rubbing element (formed by polishing material1650 and wafer piece 1640) to provide a downward force as the rubbingelement was pulled along the length of nanotube fabric layer 1610. Aforce gage 1630 was then used with pulley element 1680 to slide thepolishing material 1650 across the length of nanotube fabric layer 1610along direction 1690.

Referring now specifically to FIG. 17, the frictional force observedusing the force gage (1630 in FIG. 16) has been plotted and mapped tothe physical location of rigid rubbing element as it was pulled acrossthe nanotube fabric layer along direction 1790, which corresponds todirection 1690 in FIG. 16. As discussed above, the nanotube fabric layerstrip (1610 in FIG. 16) has been rendered into five regions. Regions1710 a, 1710 c, and 1710 e have been left substantially unordered to actas control regions for the experiment. Region 1710 b has been renderedinto an ordered network of nanotube elements oriented in a directionperpendicular to direction 1790 (that is, perpendicular to the path ofthe rubbing element). Region 1710 d has been rendered into an orderednetwork of nanotube elements oriented in a direction parallel todirection 1790 (that is, parallel to the path of the rubbing element).

As is evident within the plot of FIG. 17, as the rigid rubbing elementwas passed over the unordered nanotube fabric layer of region 1710 c,the frictional force observed was approximately 0.310 N. As the rigidrubbing element was passed over the perpendicularly oriented nanotubefabric layer (with respect to the direction of the frictional force) ofregion 1710 b, the frictional force observed was approximately 0.245 N,approximately a 21% reduction in friction with respect to controlregions 1710 a, 1710 c, and 1710 e. As the rigid rubbing element waspassed over the parallelly oriented nanotube fabric layer (with respectto the direction of the frictional force) of region 1710 d, thefrictional force observed was approximately 0.235 N, approximately a 24%reduction in friction with respect to control regions 1710 a, 1710 c,and 1710 d.

It should also be noted that while much of the present disclosuredescribes processes of rendering ordered networks of nanotube elementsfrom substantially unordered nanotube fabrics, the methods of thepresent disclosure are not limited in this regard. Indeed, the methodsof the present disclosure may also be employed to render a partiallyordered nanotube fabric layer into more highly ordered nanotube fabriclayer. For example, a rafted nanotube fabric layer (formed, for example,via the methods taught in U.S. Pat. App. No. 61/304,045 to Sen et al.)may be rendered into a fully ordered nanotube fabric layer through theapplication of a directional force as previously described in thevarious embodiments of the present disclosure.

Within certain applications a directional force may be applied over arelatively thick nanotube fabric layer. Within such applications, eventhe repeated application of a directional force may only render thosenanotubes near the surface of the thick nanotube fabric layer into anordered network of nanotube elements. That is, the resulting structuremay be described as a thin ordered nanotube fabric layer formed adjacentto a thicker unordered nanotube fabric layer. Such a structure may beused to realize an ordered nanotube fabric layer formed over a substrateelement comprising an unordered nanotube fabric layer. Within someembodiments, such a structure—an ordered nanotube fabric layer formedover an unordered nanotube fabric layer—could be further adjusted byapplying a directional force to the opposing surface of the unorderednanotube layer, rendering that opposing surface into a network ofordered nanotube elements. Within certain applications of suchembodiments, the originally deposited thick nanotube fabric layer isdeposited over a sacrificial substrate element, which is removed orotherwise volatized to allow the application of such a force to theopposing surface of the unordered nanotube fabric layer. In some aspectsof such embodiments the resulting structure might be described as twothin ordered nanotube fabric layers formed with a thicker layer ofunordered nanotube elements situated between them.

It should be noted that while a number of the figures and exampleswithin the present disclosure depict and describe processes specificallyrelated to semiconducting manufacturing, the methods of the presentdisclosure are not limited in this regard. Indeed, nanotube fabricscomprised of ordered nanotube fabric layers can be used within aplurality of systems and devices. For example, within certainembodiments such a nanotube fabric would be substantially gasimpermeable and useful within the fabrication of gas containers (suchas, but not limited to, oxygen tanks and flotation devices). Withinother embodiments such a nanotube fabric layer would be substantiallyhydrophobic and be useful as moisture resistant coatings (for example,on solar panels) or as corrosion resistant coatings. Within otherembodiments such a nanotube fabric layer would be substantiallyimpermeable to certain particulate contaminants and be useful within thefabrication of protective barrier layers. Within other embodiments sucha nanotube fabric layer would be substantially impermeable to certainbiohazardous materials (e.g., bacteria) and would be useful in thefabrication of bio-filters and the like. Within other embodiments, sucha nanotube fabric could be useful as a transparent or translucentprotective coating which could be applied over other materials (forexample over the chassis of vehicles to prevent paint scratches or asthe binding agent within safety glass. Within other embodiments, such ananotube fabric would be highly resistant to stress and wear (yet remainrelatively thin) and would be useful in the fabrication highly stressedmechanical parts (e.g., piston cylinders within internal combustionengines).

Within other embodiments, such a nanotube fabric would be highlyresistant to penetration and useful within the fabrication of punctureresistant material such as would be useful armor plating for vehicles orperson protective equipment. For example, a relatively thin orderednanotube fabric layer may be used in conjunction with a padding materialto realize a lightweight bulletproof vest. In another example, ananotube fabric may be formed over a material surface and then renderedinto an ordered network through the methods of the present disclosure torealize a relatively lightweight substantially bulletproof panel whichcould be used to armor plate a tank or car.

To this end, FIG. 18 is a perspective drawing of a multilayer nanotubefabric element 1800 comprising four individual ordered nanotube fabriclayers (1820, 1830, 1840, and 1850) and three unordered nanotube fabriclayers (1825, 1835, and 1845). Each of the four ordered nanotube fabriclayers (1820, 1830, 1840, and 1850) was deposited separately andrendered into an ordered network of nanotube elements before asubsequent nanotube fabric layer was deposited. Further, each of theordered nanotube fabric layers (1820, 1830, 1840, and 1850) was renderedinto an ordered state along a different orientation as compared withadjacent layers. That is, the first ordered nanotube fabric layer 1820was rendered into an ordered state through the use of a linear forceapplied in a first direction, and the second ordered nanotube fabriclayer 1830 was rendered into an ordered state through the use of alinear force applied in a second direction, and so on. As previouslydiscussed, within certain embodiments of the present disclosure, adirectional force applied over a relatively thick nanotube fabric layerwill tend to render only those nanotube near the surface of that layerinto an ordered network. As such, the nanotube fabric element 1800includes layers of unordered nanotube elements (1825, 1835, and 1845)remaining from the ordering processes used. In this way, a multilevelnanotube fabric element 1800 is formed comprising a plurality ofindependently ordered nanotube fabric layers (1820, 1830, 1840, and1850).

It should be noted that while the multilayer nanotube fabric element1800 (as depicted in FIG. 18) includes layers of unordered nanotubeelements (1825, 1835, and 1845) between the ordered nanotube fabriclayers (1820, 1830, 1840, and 1850), the methods of the presentdisclosure are not limited in this regard. Indeed, within the methods ofthe present disclosure each individually formed layer can be renderedinto a thick ordered nanotube fabric layer (as opposed to only thesurface of the layer being ordered) prior to the formation of asubsequent layer, essentially eliminating unordered layers (1825, 1835,and 1845). That is, a fabric layer comprised of an ordered network ofnanotube elements over its entire thickness. In some embodiments of thepresent disclosure, each individually formed layer could be kept thinenough as to ensure that the nanotube fabric layer was ordered from topto bottom during the application of a directional force prior to theformation of a subsequent layer. In other embodiments, each individuallyformed layer could be subjected to sufficient iterations of adirectional force such as to ensure that the nanotube fabric layer wasordered from top to bottom prior to the formation of a subsequent layer.

The following examples describe the rendering of several unorderednanotube fabric layers into ordered networks of individual nanotubeelements according to the methods of the present disclosure.

Within each example a purified nanotube application solution was firstrealized through the following method. Fifty grams of raw (that is,unfunctionalized) carbon nanotubes (CNTs) were refluxed inmicroelectronics grade nitric acid. Supplies of raw nanotubes (such aswere used in the following examples) may be purchased commercially froma number of vendors (e.g., Thomas Swan). The concentration of the nitricacid, the reflux time, and temperature were optimized based on thestarting CNT material. For example, CNTs were refluxed in concentratednitric acid (70%) at 120° C. for 24-30 hours. After the nitric acidreflux step, the CNT suspension in acid was diluted in 0.35 to 3% nitricacid solution (8-16 L) and taken through several passes of cross-flowfiltration (CFF). First few passes of CFF (hereinafter called CFF1) mayremove the acid and soluble metal salts in the suspension. The pH of thesuspension during the CFF1 steps was maintained at 1+/−0.3 by recoveringthe material in 0.35-3% nitric acid after each step. Typically five toeleven CFF1 steps were performed. After the CFF1 steps, the retentatewas collected in DI water and the pH of the nanotube:DI water suspensionwas increased to 8+/−0.2 with ammonium hydroxide (concentration 29%) andsonicated. This liquid was taken through another set of CFF passes(hereinafter referred as CFF2). CFF2 may remove the amorphous carbonimpurities in the solution. After the CFF2 process, the retentate wascollected in DI water and the pH of the nanotube:DI water liquid wasadjusted to pH 8+/−0.2 and the solution was sonicated for 120 minutes ina chilled sonicator bath (4-5° C.).

At this step of the process a desired concentration or optical densityof the CNT formulation can be achieved by controlling the volume of theDI water used to recover the retentate from the CFF2 membrane. Forexample if the optical density of the CNT formulation before the lastCFF2 step is 2 and the volume is 2 L, then a recovery volume of 1 L canlead to an optical density close to 4 assuming there is negligible lossin optical density through the permeate at this point. Similarly, if theoptical density of the CNT formulation before the last CFF2 step is 2and the volume is 16 L, then a recovery volume of 1 L can lead to a CNTformulation of optical density 32. The concentration of the CNTformulation (optical density) that can be practically achieved isdependent on, but is not limited to, the starting CNT charge used in thereaction, the reaction conditions, number of CFF steps, CFF membranepore size, CFF membrane surface area, and pH.

Finally, the solution was centrifuged two or three times at about70000-100000 g for about 20-30 min each. In certain cases, the pH of thesolution was adjusted to 8+/−0.2 in between the centrifugation passeswhich may remove residual metal or carbon nanoparticles in the liquid bysedimentation. After the centrifugation step, the supernatant wascollected and used as the final purified nanotube application solution.The concentration of the final nanotube application solution depends onthe centrifugation conditions used. Typically for a spin coatapplication CNT solutions with an optical density projected to beapproximately 20+/−5 and a pH of 7+/−0.5 were used.

Further, within each of the following examples, this purified nanotubeapplication solution was then spun coat over a substrate layer to forman unordered nanotube fabric layer. Specifically, three spin coatingoperations were performed to form the nanotube fabric layers of examples1, 2, 3, 5, 7, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, and 20, four spincoating operation were performed to form the nanotube fabric layers ofexamples 4 and 8, one spin coating operation was performed to form thenanotube fabric layer of example 6, and five spin coating operationswere performed to form the nanotube fabric layer of example 15. Thenanotube fabric layer of examples 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 16,17, 17, 19, and 20 were formed over a silicon dioxide substrate. Thenanotube fabric layer of example 10 was formed over a 1018 low carbonsteel substrate. The nanotube fabric layer of example 12 was formed overa polyethylene terephthalate (PET) substrate. The nanotube fabric layerof example 14 was formed over a 2024 aluminum alloy substrate. Thenanotube fabric layer of example 15 was formed over a titanium nitride(TiN) substrate.

For all examples, the spin coating operations were as follows. A rawwafer was pre-baked on a 300° C. hot plate for five minutes.Approximately 3 ml of the adjusted solution was dispensed onto the wafervia a plastic pipette while the wafer was rotated at 60 rpm. Afterthirty seconds, the spin speed was increased to 500 rpm for two seconds,then subsequently reduced to fifty rpm for 180 seconds, and finallyincreased to 2000 rpm for twenty seconds. For examples 1-14, the waferwas placed on a 300° C. hot plate for two minutes between each spincoating operation. For example 15, the wafer was placed in a 500° C.environment for five minutes between each spin coating operation. Aftera cool down cycle, the entire process was repeated again twice such asto apply the desired number of coats of the application solution overthe wafer.

Once an unordered nanotube fabric layer was formed over the surface of awafer, a directional force was applied over the surface of the fabriclayer (as detailed in each of the following examples) in order to renderat least a portion of the nanotube fabric layer into an ordered networkof nanotube elements. Within an example 20 an additional layer ofsilicon nanowires was applied over the surface of the nanotube fabriclayer (via a spin coating operation, as described below) prior to theapplication of a directional force. Finally an anneal process (625° C.for thirty minutes) was performed.

Example 1

FIGS. 19A-19C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (1901, 1902, and 1903 respectively) firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of adirectional rolling force along the direction indicated within each SEMimage. The rolling force was applied via a steel hand roller, rolleddirectly against the nanotube fabric layer fifty times with lightpressure (approximately two Newtons). As is evident in FIG. 19A (the10,000× magnification image), the resulting nanotube fabric layer wasrendered into an ordered state oriented along the direction of theapplied rolling force.

Example 2

FIGS. 20A-20C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (2001, 2002, and 2003 respectively) firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of adirectional rubbing force along the direction indicated within each SEMimage. The rubbing force was applied by placing the wafer facedown on aTEFLON or polytetrafluoroethylene sheet (such that the nanotube fabriclayer was in direct contact with the TEFLON or polytetrafluoroethylenesheet), placing a 150 g weight on the reverse side (that is, thenon-coated side) of the wafer, and sliding the wafer along the TEFLON orpolytetrafluoroethylene sheet a distance of approximately five inchesfifteen times. As is evident in FIG. 20A (the 5,000× magnificationimage), the nanotube fabric layer exhibited thin bands (on the order of2 μm across) of ordered nanotubes resulting from the applied rubbingforce.

Example 3

FIGS. 21A-21C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (2101, 2102, and 2103 respectively) firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of adirectional rubbing force along the direction indicated within each SEMimage. The rubbing force was applied by placing the wafer facedown on aTEFLON or polytetrafluoroethylene sheet (such that the nanotube fabriclayer was in direct contact with the TEFLON or polytetrafluoroethylenesheet), placing a 150 g weight on the reverse side (that is, thenon-coated side) of the wafer, and sliding the wafer along the TEFLON orpolytetrafluoroethylene sheet a distance of approximately five inchestwenty-five times. As is evident in FIG. 21A (the 5,000× magnificationimage), the resulting nanotube fabric layer was rendered into an orderedstate oriented along the direction of the applied rubbing force.

Example 4

FIGS. 22A-22C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (2201, 2202, and 2203 respectively) firstformed via four spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of adirectional rubbing force along the direction indicated within each SEMimage. The rubbing force was applied by placing the wafer facedown on a300 mm silicon dioxide wafer (such that the nanotube fabric layer was indirect contact with the silicon dioxide wafer surface), placing a 150 gweight on the reverse side (that is, the non-coated side of the wafer),and sliding the wafer along silicon dioxide wafer a distance ofapproximately four inches 250 times. As is evident in FIG. 22A (the5,000× magnification image), the resulting nanotube fabric layer wasrendered into an ordered state oriented along the direction of theapplied rubbing force.

Example 5

FIGS. 23A-23C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (2301, 2302, and 2303 respectively) firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of anarcing rubbing force along the direction indicated within each SEMimage. The rubbing force was applied by passing a wool rubbing pad overthe wafer in an arcing motion 100 times. The wool rubbing pad was notrotated as it was passed over the wafer. As is evident in FIG. 23A (the10,000× magnification image), the resulting nanotube fabric layer wasrendered into an ordered state oriented in a substantially lineardirection substantially tangent to the initial angle of the appliedarcing force. As evident in FIG. 23B (the 25,000× magnification image),despite the arcing direction of the applied rubbing force the nanotubeelements were ordered in a generally linear orientation.

Example 6

FIGS. 24A-24C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (2401, 2402, and 2403 respectively) firstformed via a single spin coating operation of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of alinearly applied polishing force along the direction indicated withineach SEM image. The polishing force was applied by passing a cylindricalvelour roller over the wafer in a linear motion 50 times. Thecylindrical velour roller was rotated at a speed of 60 rpm and passedover the wafer at a constant rate of approximately 0.4 inches per secondfor each pass. As is evident in FIG. 24C (the 75,000× magnificationimage), the resulting nanotube fabric layer was rendered into an orderedstate oriented along the direction of the applied polishing force.

Example 7

FIGS. 25A-25C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (2501, 2502, and 2503 respectively) firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of arotational polishing force along the direction indicated within each SEMimage. The polishing force was applied by positioning a round woolpolishing pad over the wafer and rotating the polishing pad at a rate ofsixty rotations per minute for ninety seconds. As is evident in FIG. 25B(the 25,000× magnification image), the resulting nanotube fabric layerwas rendered into several regions of ordered nanotube elements orientedin along several directions.

Example 8

FIGS. 26A-26C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (2601, 2602, and 2603 respectively) prior tobeing rendered into an ordered state by the methods of the presentdisclosure. The nanotube fabric layer depicted in FIGS. 26A-26C wasformed via four spin coating operations of a purified nanotubeapplication solution (as described above) over a Si wafer. The depositednanotube fabric layer was then rendered into an ordered network ofnanotube elements through the application of a linear rubbing force. Thelinear rubbing force was applied by sliding a weighted CMP pad(approximately 75 g) along the length of the nanotube fabric layer 20times. FIGS. 27A-27B are SEM images of the same nanotube fabric layerdepicted in FIGS. 26A-26C after this linear rubbing force was appliedalong the direction indicated in FIGS. 27A-27C. As is evident in FIG.27C (the 75,000× magnification image), the resulting nanotube fabriclayer was rendered into an ordered network of nanotube elements orientedin direction of the applied force.

Example 9

FIGS. 28A-28C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (2801, 2802, and 2803 respectively) firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application ofcryokinetic impingement operation along the direction indicated withineach SEM image. FIG. 28D is an SEM image 2804 of the formed nanotubefabric layer prior to the application of the cryokinetic impingementoperation illustrating the substantially unordered state of the nanotubefabric layer prior to the application of the polishing force. Once thenanotube fabric layer was formed on the silicon substrate, a protectiveplastic layer (Saran wrap, based upon polyvinylidene chloride) waspositioned over the fabric layer. Then a cryokinetic impingement gun (acommercial dry ice cleaning system available from Va-Tran System, Inc.)was used to spray frozen pellets of carbon dioxide for ten passes. Eachpass included sweeping the spray across the wafer surface (protected bythe plastic layer) for ten seconds. Between each pass, the protectiveplastic layer was given time to defrost (on the order of thirtyseconds). As is evident in FIG. 28C (the 75,000× magnification image),the resulting nanotube fabric layer was rendered into an ordered stateoriented along the direction of the applied cryokinetic impingementforce.

Example 10

FIGS. 29A-29C are SEM images depicting the formation and subsequentordering of an exemplary nanotube fabric layer formed over a 1018 lowcarbon steel substrate. FIG. 29A is an SEM image 2901 of the steelsubstrate prior to the deposition of the nanotube fabric layer. FIG. 29Bis an SEM image 2902 of the exemplary nanotube fabric layer (in asubstantially unordered state) formed via three spin coating operationsof a purified nanotube application solution (as described above). FIG.29C is an SEM image 2903 of the exemplary nanotube fabric layer afterbeing rendered into an ordered network of nanotube elements through theapplication of a directional rubbing force along the direction indicatedwithin SEM image 2903. Machining grooves along the surface of the steelsubstrate are visible in all three SEM images (2901, 2902, and 2903)running orthogonal to the indicated direction of the applied rubbingforce (shown in SEM image 2903). The rubbing force was applied byplacing the wafer face down on a rayon polishing pad (that is, placingthe wafer such that the nanotube fabric layer was positioned in directphysical contact with the rayon polishing pad) and sliding the waferapproximately six to eight inches along the surface of the pad fiftytimes. The rayon polishing pad used within this example was a South BayTechnology, Inc. p/PRF12A-10 “rayon-fine polishing cloth.” As is evidentin FIG. 29C, the resulting nanotube fabric layer was rendered into anordered state oriented along the direction of the applied rubbing force.

Example 11

FIGS. 30A-30C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (3001, 3002, and 3003 respectively) firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application ofpiezoelectric generated rubbing force along the direction indicatedwithin each SEM image. FIG. 30D is an SEM image 3004 of the formednanotube fabric layer prior to the application of the piezoelectricgenerated rubbing force illustrating the substantially unordered stateof the nanotube fabric layer prior to the application of the rubbingforce. Once the nanotube fabric layer was formed on the siliconsubstrate, a protective plastic layer (Saran wrap, based uponpolyvinylidene chloride) was positioned over the fabric layer. Then ay-poled piezoelectric crystal element was placed over the plastic layersuch that the element covered substantially the entire nanotube fabriclayer. A 1.25 pound weight was then place over the piezoelectric crystalelement (using a layer of PTFE film to provide electrical isolationbetween the weight and the piezoelectric crystal) such as to maintainsufficient pressure between the crystal element and the nanotube fabriclayer. The piezoelectric crystal element was then driven by a piezoamplifier at 11 kHz, 10 V (peak to peak) for 2.5 hours. The directionindicated in SEM images 2901, 2902, and 2903 is representative of theaxis of vibration of the piezoelectric crystal element. As is evident inFIG. 30C (the 75,000× magnification image), the resulting nanotubefabric layer was rendered into an ordered state oriented along thedirection of vibration.

Example 12

FIGS. 31A-31C are SEM images at different magnifications (3101, 3102,and 3103 respectively) of an exemplary nanotube fabric layer formed overa polyethylene terephthalate (PET) substrate and rendered into anordered network of nanotube elements through the application of adirectional rubbing force along the direction indicated within each SEMimage. The rubbing force was applied by placing the wafer face down on arayon polishing pad (that is, placing the wafer such that the nanotubefabric layer was positioned in direct physical contact with the rayonpolishing pad) and sliding the wafer approximately six to eight inchesalong the surface of the pad fifty times. The rayon polishing pad usedwithin this example was a South Bay Technology, Inc. p/PRF12A-10“rayon-fine polishing cloth.” As is evident in FIG. 31C (the 75,000×magnification image), the resulting nanotube fabric layer was renderedinto an ordered state oriented along the direction of the appliedrubbing force.

Example 13

FIGS. 32A-32C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (3201, 3202, and 3203 respectively) firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of highpressure air flow polishing operation along the direction indicatedwithin each SEM image. FIG. 32D is an SEM image 3204 of the formednanotube fabric layer prior to the application of the high pressure airflow polishing operation illustrating the substantially unordered stateof the nanotube fabric layer prior to the application of the polishingforce. Once the nanotube fabric layer was formed on the siliconsubstrate, a protective plastic layer (Saran wrap, based uponpolyvinylidene chloride) was positioned over the fabric layer. Then anair gun (a commercial precision safety air gun available from Exair,model number 1410SS fitted with a “nano supper air” nozzle, model number1110SS) was used to flow nitrogen gas (N2) at 100 psi over the nanotubefabric layer for twelve sweeps. Each sweep included moving the air gunacross the wafer surface (protected by the plastic layer) in a “zig zag”pattern for approximately ten seconds. As is evident in FIG. 32C (the75,000× magnification image), the resulting nanotube fabric layer wasrendered into an ordered state oriented along the direction of the airflow.

Example 14

FIGS. 33A-33B are SEM images depicting the ordering of an exemplarynanotube fabric layer formed over a 2024 aluminum alloy substrate. FIG.33A is an SEM image 3301 of an exemplary nanotube fabric layer (in asubstantially unordered state) formed via three spin coating operationsof a purified nanotube application solution (as described above). FIG.33B is an SEM image 3302 of the exemplary nanotube fabric layer afterbeing rendered into an ordered network of nanotube elements through theapplication of a directional rubbing force along the direction indicatedwithin SEM image 3302. The rubbing force was applied by placing thewafer face down on a rayon polishing pad (that is, placing the wafersuch that the nanotube fabric layer was positioned in direct physicalcontact with the rayon polishing pad) and sliding the waferapproximately six to eight inches along the surface of the pad fiftytimes. The rayon polishing pad used within this example was a South BayTechnology, Inc. p/PRF12A-10 “rayon-fine polishing cloth.” As is evidentin FIG. 33B, the resulting nanotube fabric layer was rendered into anordered state oriented along the direction of the applied rubbing force.

It should be noted that the surface of the 2024 aluminum alloy substrateshows large pores in the aluminum oxide surface coating where thenanotube elements within the nanotube fabric layer are recessed from thesurface. The nanotube elements within these pore regions show littleevidence of alignment whereas the nanotube elements on the surface (thatis, those nanotube elements not within the pores) of the denser aluminumoxide surface shows a very high degree of alignment. This suggests thatcontact with the fabric was an important aspect in aligning this sample.

Example 15

FIGS. 34A-34C are SEM images of an exemplary nanotube fabric layer atdifferent magnifications (3401, 3402, and 3403 respectively) firstformed via five spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of adirectional rubbing force along the direction indicated within each SEMimage. The rubbing force was applied by placing the wafer facedown on a20″ ROHM HAAS SPM3100 CMP pad (such that the nanotube fabric layer wasin direct contact with the cmp pad surface). Prior to the start of therubbing operation, the wafer—loaded into the head of a CMP machine—wassprayed with deionized water to provide a lubricating medium at theinterface between the nanotube fabric layer on the wafer surface and theCMP pad. The CMP head passed the wafer back and forth over the CMP padin a maximum stroke length of 1.6 inches at a rate of ten strokes/minutefor five minutes. The CMP pad was not rotated as the wafer was rubbedacross its surface. As is evident in FIG. 34C (the 75,000× magnificationimage), the nanotube fabric layer was rendered into an ordered stateoriented along the direction of the applied rubbing force.

Example 16

FIG. 35 is an AFM image 3501 of an exemplary nanotube fabric layer firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of arubbing force via an electronically controlled linear actuator. Withinthe present example, a Newton linear actuator (model no. CMA 12CCCL) wasdriven with a Newport universal motion controller driver (model no. ESP300) to translate a silicon wafer back and forth over the surface of theexemplary nanotube fabric layer. Both the actuator and the motioncontroller driver are available from Newport Corporation of Irvine,Calif., and the use of such equipment is well known to those skilled inthe art. The silicon wafer was translated a distance of 1 mm with eachstroke for a total of one hundred iterations. The assembly also provideda downward force (that is a force pressing the silicon rubbing surfaceagainst the nanotube fabric layer) of 38 g. As is evident in FIG. 35,the nanotube fabric layer was rendered into an ordered state orientedalong the direction of the applied rubbing force.

Example 17

FIG. 36 is an AFM image 3601 of an exemplary nanotube fabric layer firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of arubbing force via an electronically controlled linear actuator. Withinthe present example, a Newton linear actuator (model no. CMA 12CCCL) wasdriven with a Newport universal motion controller driver (model no. ESP300) to translate a silicon wafer back and forth over the surface of theexemplary nanotube fabric layer. Both the actuator and the motioncontroller driver are available from Newport Corporation of Irvine,Calif., and the use of such equipment is well known to those skilled inthe art. The silicon wafer was translated a distance of 0.1 mm with eachstroke for a total of one thousand iterations. The assembly alsoprovided a downward force (that is a force pressing the silicon rubbingsurface against the nanotube fabric layer) of 42 g. As is evident inFIG. 36, the nanotube fabric layer was rendered into an ordered stateoriented along the direction of the applied rubbing force.

Example 18

FIG. 37 is an AFM image 3701 of an exemplary nanotube fabric layer firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of arubbing force via an electronically controlled linear actuator. Withinthe present example, a Newton linear actuator (model no. CMA 12CCCL) wasdriven with a Newport universal motion controller driver (model no. ESP300) to translate a silicon wafer back and forth over the surface of theexemplary nanotube fabric layer. Both the actuator and the motioncontroller driver are available from Newport Corporation of Irvine,Calif., and the use of such equipment is well known to those skilled inthe art. The silicon wafer was translated a distance of 0.05 mm witheach stroke for a total of one thousand iterations. The assembly alsoprovided a downward force (that is a force pressing the silicon rubbingsurface against the nanotube fabric layer) of 80 g. As is evident inFIG. 37, the nanotube fabric layer was rendered into an ordered stateoriented along the direction of the applied rubbing force.

Example 19

FIG. 38 is an AFM image 3801 of an exemplary nanotube fabric layer firstformed via three spin coating operations of a purified nanotubeapplication solution (as described above) and then rendered into anordered network of nanotube elements through the application of arubbing force via an electronically controlled linear actuator. Withinthe present example, a Newton linear actuator (model no. CMA 12CCCL) wasdriven with a Newport universal motion controller driver (model no. ESP300) to translate a silicon wafer back and forth over the surface of theexemplary nanotube fabric layer. Both the actuator and the motioncontroller driver are available from Newport Corporation of Irvine,Calif., and the use of such equipment is well known to those skilled inthe art. The silicon wafer was translated a distance of 0.01 mm witheach stroke for a total of one thousand iterations. The assembly alsoprovided a downward force (that is a force pressing the silicon rubbingsurface against the nanotube fabric layer) of 28 g. As is evident inFIG. 38, the nanotube fabric layer was rendered into an ordered stateoriented along the direction of the applied rubbing force.

Example 20

FIGS. 39A-39D are SEM images depicting the formation and subsequentordering of an exemplary nanotube fabric layer along with an exemplarylayer of silicon nanowires. FIG. 39A is an SEM image 3901 of anexemplary nanotube fabric layer first formed via three spin coatingoperations of a purified nanotube application solution over a siliconwafer (as described above) and then coated with a layer of siliconnanowires. Specifically, monodispersed silicon nanowires (available fromSigma-Aldrich, Inc of St. Louis, Mo., model no. 730866) were applieddropwise to the formed nanotube fabric layer. Thirty drops were applied,with each drop being allowed to air dry before the subsequent drop wasapplied. After all thirty drops had been applied, the silicon wafer (nowcoated with the nanotube fabric layer and the layer of siliconnanowires) was baked at 300° C. for two minutes. FIGS. 39B-39D are SEMimages of the exemplary nanotube fabric and silicon nanowire layer atdifferent magnifications (3902, 3904, and 3904 respectively) after beingrendered into an ordered network of nanotube elements through theapplication of a directional rubbing force. The rubbing force wasapplied by placing the wafer face down on a rayon polishing pad (thatis, placing the wafer such that the nanotube fabric and silicon nanowirelayer was positioned in direct physical contact with the rayon polishingpad) and sliding the wafer approximately four inches along the surfaceof the pad thirty times. The rayon polishing pad used within thisexample was a South Bay Technology, Inc. p/PRF12A-10 “rayon-finepolishing cloth.” As is evident in FIG. 39C (the 10,000× magnificationimage), both the nanotube fabric layer and the silicon nanowires wererendered into an ordered state oriented along the direction of theapplied rubbing force. The present example demonstrates the generalityof the methods of the present disclosure for use in ordering high aspectratio nanoscopic structures (including, but not limited to, nanotubesand nanowires).

We have described multiple techniques to minimize or substantiallyeliminate gaps and voids within a nanotube fabric. The techniques alsocan be said to control the positioning of the nanotubes within thefabric, to control the positions of gaps within the nanotube fabric, andto control the concentration of the nanotubes within the fabric. Forexample, these techniques can provide low porosity, high densityfabrics. Further, the techniques can be described as controlling thegaps of nanotubes within the nanotube fabric. Thus, we have disclosedtechniques to create devices sized to and smaller than the currentlithography limits (for example, less than or equal to about 20 nm). Lowporosity, high density fabrics also can be created by, for example,filling gaps in the nanotube film with additional nanotube elements.

Further, we have described a plurality of methods and apparatus fortranslating a directional force over a nanotube fabric layer. Theselection and use of one or more of these methods in an orderingoperation should, in most applications of the methods of the presentdisclosure, be limited only to such methods and apparatus which do notdamage or otherwise ablate the nanotubes within the nanotube fabriclayer being operated on.

Further, it should be understood to one of skill in the art that theordered nanotube fabrics produced by the methods disclosed herein can beused in any device, article or process where a thin, strong, durablefilm is required for a certain function. For example, the methods of thepresent disclosure are useful for any application using nanotube fabricswherein the concentration of the nanotube elements within the fabric orthe number or size of gaps within the fabric are required to fit withina preselected tolerance.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention not be limited by thespecific disclosure herein, but rather be defined by the appendedclaims; and that these claims will encompass modifications of andimprovements to what has been described.

What is claimed is:
 1. A method for arranging nanotube elements within ananotube fabric, comprising: providing a plurality of nanotube elementsover a material layer to obtain a substantially dry, fully formed, fixednanotube fabric comprising a plurality of nanotube elements in a firstoperation, wherein said nanotube fabric is substantially free of anysuspension medium; and translating a rotational force over at least aportion of said substantially dry, fully formed, fixed nanotube fabricin a second operation to arrange at least a portion of said nanotubeelements into an ordered network; wherein said second operation isperformed subsequent to said first operation; and wherein saidrotational force arranges said nanotube elements within said portion ofsaid nanotube fabric into a plurality of ordered regions, wherein eachordered region is comprised of nanotube elements in a substantiallyuniform orientation.
 2. The method of claim 1 wherein said rotationalforce is applied over said portion of said portion of said nanotubefabric at least once.
 3. The method of claim 1 further comprisingrepeatedly applying said rotational force to said portion of saidnanotube fabric.
 4. The method of claim 1 wherein said material layer isrigid.
 5. The method of claim 4 wherein said material layer is selectedfrom a group consisting of elemental silicon, silicon oxide, siliconnitride, silicon carbides, PTFE, organic polymers, pvc, styrenes,polyvinyl alcohol, polyvinyl acetate, hydrocarbon polymers, inorganicbackbone, boron nitride, gallium arsenide, group III/V compounds, groupII/VI compounds, wood, metals, metal alloys, metal oxides, ceramics, andglass.
 6. The method of claim 1 wherein said material layer is a rigidstructural composite.
 7. The method of claim 1 wherein said materiallayer is flexible.
 8. The method of claim 7 wherein said material isselected from a group consisting of polyethylene terephthalate (PET),polymethylmethacrylate, polyamides, polysulfones, and polycyclicolefins.
 9. The method of claim 1 wherein applying said rotational forcearranges at least a portion of said nanotube fabric into a preselectedorientation within at least one preselected region of said nanotubefabric.
 10. The method of claim 1 further comprising depositing alubricating medium over a portion of said nanotube fabric prior to saidapplication of said rotational force.
 11. The method of claim 10 whereinsaid lubricating medium is comprised of at least one material selectedfrom the list consisting of water, halocarbon liquids, liquefied gases,hydrocarbon liquids, functionalized organic liquids, organo-siloxanebased cyclics, linear liquids, molybdenum disulfide, boron nitride,graphite, and styrene beads.
 12. The method of claim 1 wherein saidnanotube fabric is formed via one of a spin coating operation, a spraycoating operation, a dip coating operation, a silk screen printingoperation, or a gravure printing operation.
 13. The method of claim 1wherein said nanotubes are carbon nanotubes.
 14. The method of claim 1wherein said nanotube fabric is a composite mixture of carbon nanotubesand other materials.
 15. The method of claim 14 wherein said othermaterials are selected from the group consisting of buckyballs,amorphous carbon, silver nanotubes, quantum dots, colloidal silver,monodisperse polystyrene beads, and silica particles.
 16. The method ofclaim 1 wherein said nanotube elements are functionalized carbonnanotubes.
 17. The method of claim 16 wherein said functionalized carbonnanotubes are carbon nanotubes affixed with moieties which provide anelectrically insulating barrier over the sidewalls of said carbonnanotubes.
 18. The method of claim 17 wherein said moieties are organicfunctional groups.
 19. The method of claim 17 wherein said moieties aresilicon functional groups.
 20. The method of claim 17 wherein saidmoieties include at least one of organosilicate, silicon oxide, organosilicon oxide, methylsilsequioxane, hydrogen silsequioxane,organosiloxane, dimethylsiloxane/polyorgano ether, organopolymer, DNA,and polyamide.
 21. The method of claim 1 wherein said rotational forceis applied through a polishing element.
 22. The method of claim 21wherein said polishing element in rotated within a plane parallel tosaid nanotube fabric layer.
 23. The method of claim 21 wherein saidpolishing element comprises at least one of polyester microfiber,polyamide microfiber, polyester, polyamide, styrene, polyvinylalcoholfoam, cotton, wool, cellulose, and rayon.
 24. The method of claim 1wherein said rotational force is applied to said nanotube fabric throughan intervening material.
 25. The method of claim 1 wherein said orderedregions are substantially free of gaps and voids.
 26. The method ofclaim 1 wherein the orientation of nanotube elements within said orderedregions is responsive to the direction of said applied rotational force.27. A method for arranging nanotube elements within a nanotube fabric,comprising: providing a plurality of nanotube elements over a materiallayer to obtain a substantially dry, fully formed, fixed nanotube fabriccomprising a plurality of nanotube elements in a first operation,wherein said nanotube fabric is substantially free of any suspensionmedium; and translating a rotational force over at least a portion ofsaid substantially dry, fully formed, fixed nanotube fabric in a secondoperation to arrange at least a portion of said nanotube elements intoan ordered network; wherein said second operation is performedsubsequent to said first operation; and wherein said rotational forcearranges said nanotube elements such that said portion of said nanotubefabric is substantially free of gaps and voids.